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Finance

Loans, savings, investing and everyday money maths. Every rate, term and price is an input you control, so nothing here is tied to a particular year’s figures.

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Loan payment & amortisationRepayment on a fixed-rate amortised loan, with a year-by-year schedule.Mortgage repaymentFull monthly housing cost: principal, interest, rates, insurance and strata.Compound interestGrowth of a lump sum plus regular contributions.Simple interestInterest charged on the original principal only.Savings goalWhat you must put away each month to hit a target.Present & future valueWhat a future sum is worth today, and vice versa.Annuity / drawdown payoutHow much a pot pays out each month until it runs dry.Retirement projectionBalance at retirement and how long it lasts.Car loanRepayment after deposit, trade-in and on-road costs.Credit card payoffHow long a balance takes to clear at a fixed payment.APR to effective rate (APY)Converts a nominal rate into the true annual yield.Inflation & purchasing powerWhat money is worth after years of price rises.Return on investmentTotal and annualised return on an investment.CAGR (compound annual growth rate)The smooth yearly rate that links a start and end value.NPV & IRRDiscounted value of a project, and the rate that makes it break even.Rule of 72Quick mental estimate of doubling time.Salary & hourly rate converterMoves between hourly, weekly, monthly and annual pay.Tip & bill splitTip amount and what each person owes.Discount & sale pricePrice after one or two discounts, and what you save.Sales tax / GST / VATAdds tax to a net price, or strips it out of a gross one.Margin & markupTurns cost and price into margin, markup and profit.Break-even pointUnits and revenue needed before a business turns a profit.Debt-to-income ratioThe ratio lenders use to size your borrowing.How much can I borrowMaximum loan a given repayment supports.Bond price & yieldPresent value of a bond’s coupons and face value.Average share cost & positionBlended entry price across several buys.Currency conversion with feesWhat you actually receive after spread and fixed fees.Dividend yieldWhat a stock pays each year as a percentage of its share price, plus yield on cost.GDP per capitaA country’s economic output divided evenly across its population.Net to gross payThe gross amount needed to leave a chosen net (take-home) figure, at a deduction rate you set.Quick Ratio CalculatorThe quick (acid-test) ratio: whether the most liquid current assets can cover current liabilities.PayPal Fees CalculatorPayPal transaction fee and the amount you actually receive, from an editable percentage and fixed fee.Money CounterTotal cash value from a count of Australian notes and coins, by denomination.COGS (Cost of Goods Sold)Cost of goods sold from beginning inventory, purchases and ending inventory.Marginal CostThe extra cost of producing more units, from total cost and quantity at two output levels.Purchasing power parity (implied rate)Implied PPP exchange rate from the price of the same basket of goods in two currencies, compared with the market rate.Deadweight Loss CalculatorEstimates deadweight loss as the area of the loss triangle from a quantity reduction and the resulting price gap.Discount Rate CalculatorSolves for the discount rate implied by a present value, a future value and a number of periods.50/30/20 budget ruleSplits after-tax income into needs, wants and savings using the 50/30/20 framework.Consumer surplusThe value buyers gain from paying less than the most they were willing to pay.Dividend incomeTotal dividend income from shares held and the dividend paid per share, plus the yield.Real estate commissionWhat an agent earns on a property sale from the sale price and the agreed commission rate.Depreciation (straight-line & declining)Annual depreciation expense and remaining book value under two common methods.Payback periodHow many years of cash flows it takes to recover an initial investment, plain and discounted.Liquidity ratios (current, quick & cash)Three views of whether current assets can cover current liabilities.Leverage & solvency ratiosHow much of a company is financed by debt, and how easily it covers interest.Working capital & turnoverThe cash cushion between current assets and current liabilities, and how hard it is working.Cash conversion cycleDays between paying for inventory and collecting cash from its sale.WACC (weighted average cost of capital)The blended return a company must earn to satisfy both lenders and shareholders.CAPM (cost of equity)The return shareholders should require, given the market risk a stock carries.Dividend discount model (Gordon growth)Values a stock as its dividends, discounted and growing forever.Dividend yield & payout ratioWhat a stock pays relative to its price, and how much of earnings that consumes.EBITDA & marginOperating profitability before interest, tax, depreciation and amortisation.Enterprise valueThe theoretical takeover price of a company: equity plus debt, minus cash on hand.Stock valuation multiples (P/E, P/B, PEG)Common price ratios used to judge whether a stock is cheap or expensive.DuPont analysis (ROE breakdown)Splits return on equity into profitability, efficiency and leverage.Sharpe ratioReturn earned above the risk-free rate, per unit of volatility taken on.Perpetuity valuePresent value of a cash flow that continues forever, flat or growing.Balloon loan paymentRegular instalment on a loan amortised over a long schedule, plus the lump sum due early.Sustainable growth rateThe fastest a company can grow using only retained profit, no new borrowing or share issues.Graham numberBenjamin Graham’s quick estimate of a fair share price from earnings and book value.Profit CalculatorTotal dollar profit from revenue minus cost of goods sold and other costs, plus the resulting margin.MPC (Marginal Propensity to Consume) CalculatorMarginal propensity to consume from a change in consumption and a change in income, plus the implied propensity to save.Liquid Net Worth CalculatorNet worth from cash and easily-sold assets only, kept separate from illiquid holdings.Price Elasticity of Demand CalculatorHow much quantity demanded responds to a price change, from an old and new price and quantity.Pro rata rentProportional rent owed for a partial period, from the full period rent and days actually occupied.Return on Equity CalculatorReturn on equity (ROE) from net income and shareholders’ equity, the profit generated per dollar of equity.Commission CalculatorCommission earned on a sale from the sale amount and commission rate, plus any base pay.Contribution Margin CalculatorContribution margin per unit and as a ratio, from selling price and variable cost, plus break-even units against fixed costs.PayPal Exchange Rate CalculatorCompares the amount PayPal converts at its own exchange rate against the underlying market rate, using an editable markup.Revenue CalculatorTotal revenue from price per unit and quantity sold, with an optional second product line added in.Marginal RevenueThe extra revenue from selling one more unit, from total revenue and quantity at two output levels.Opportunity CostThe value of the next-best alternative given up when choosing one option over another.Unemployment RateThe share of the labour force that is unemployed, from the number unemployed and the total labour force.Real Rate of ReturnThe inflation-adjusted return on an investment, using the Fisher equation rather than a simple subtraction.Income Elasticity of Demand CalculatorHow much quantity demanded responds to a change in income, from an old and new income and quantity.Bond yield to maturity (YTM)The return a bond earns if held to maturity, found by solving price for yield.Bond duration & convexityHow sensitive a bond’s price is to a change in yield, to first and second order.Yield to call (YTC)Approximate return on a callable bond if the issuer redeems it early.Cap rate (capitalisation rate)The unlevered return a rental property generates from its net operating income.Gross rent multiplier (GRM)A quick screen of property price against the rent it collects, before expenses.DSCR (debt service coverage ratio)Whether a property or business generates enough income to cover its debt payments.Asset turnover ratiosHow hard a company’s inventory, receivables and total assets are working to generate revenue.Free cash flow & yieldCash a business generates after the capital spending needed to keep running.Rent or buy comparisonNet cost of renting versus buying a home over the years you plan to stay.Car lease payment (money factor)Monthly lease payment from depreciation and finance charges.Real interest rate (Fisher equation)What an interest rate is worth once expected inflation is stripped out.PVGO (present value of growth opportunities)How much of a stock’s price reflects expected future growth, versus current earnings alone.Growing annuity present valuePresent value of a stream of payments that increases by a fixed rate each period.Degree of operating leverage (DOL)How much operating profit swings for a given swing in sales, given a company’s fixed cost base.Revenue valuation multiples (EV/Sales & P/S)Prices a company against its revenue, useful when earnings are thin or negative.Debt-to-capital ratioWhat share of a company’s permanent funding comes from debt rather than equity.Interest-only mortgageThe interest-only payment, and what it jumps to once principal repayments begin.Biweekly mortgage paymentTime and interest saved by paying half the monthly payment every two weeks instead.Price Elasticity of Supply CalculatorHow much quantity supplied responds to a price change, from an old and new price and quantity.Loss Ratio CalculatorInsurance loss ratio: claims paid as a percentage of premiums earned.EBIT CalculatorEarnings before interest and tax, from net income, interest and tax, with the resulting margin.Price per Square Metre CalculatorPurchase price divided by floor area in square metres, plus the price at a target rate per m².Basis Points CalculatorConverts basis points to a percentage or decimal, or a percentage back to basis points, both directions.P/E Ratio CalculatorPrice-to-earnings ratio from a share price and earnings per share, with the equivalent earnings yield.Earnings per Share CalculatorNet income per outstanding share, the building block behind the P/E ratio and other stock metrics.Interest Coverage Ratio CalculatorHow many times over a business can pay its interest bill from operating earnings (EBIT).Average Share PriceWeighted average price you paid across several share purchases at different prices and quantities.PV of AnnuityPresent value of a series of equal, regular payments, from the payment amount, interest rate and number of periods.Margin of Safety CalculatorHow far actual or budgeted sales can fall before a business hits its break-even point, in dollars and as a percentage.Dividend Per Share CalculatorDividend per share (DPS) from total dividends paid, preferred dividends and shares outstandingMarket CapMarket capitalisation of a company from its share price and total shares outstanding.GDP DeflatorCalculates the GDP deflator from nominal and real GDP, the broadest measure of economy-wide price change.Inventory Turnover CalculatorInventory turnover ratio and days-to-sell from cost of goods sold and average inventory value.Effective Interest Rate CalculatorEffective annual rate from a nominal rate and compounding frequency, or the nominal rate needed for a target effective rate.Credit utilization ratioHow much of your available credit is in use, per card and overall.Bond equivalent yieldConverts a discount instrument price into an annualised coupon-style yield.Taxable equivalent yieldThe taxable yield needed to match a tax-free bond after tax.Insurance combined ratioWhether premiums collected cover claims and the cost of writing policies.Balance transfer savingsWhether moving a balance to a promo-rate card actually saves money.Blended interest rateThe single weighted rate that several loans are effectively costing.Sortino ratioRisk-adjusted return that only penalises downside volatility.Maximum drawdownThe worst peak-to-trough decline across a series of portfolio values.Modified internal rate of return (MIRR)A more realistic IRR that uses separate finance and reinvestment rates.Debt snowball vs avalancheCompares paying off smallest balances first against paying off highest rates first.Net effective rentThe real average rent after free months, allowances and operating costs.Days cash on handHow many days a business could cover its operating costs from cash reserves.Weighted average shares outstandingTime-weighted share count used as the denominator for EPS.Buyback impact on EPSHow a share repurchase changes earnings per share, all else equal.Annuity due vs ordinary annuityHow payment timing (start vs end of period) changes an annuity’s value.Economic value added (EVA)Profit left over after paying for the capital used to generate it.Reverse CAGR CalculatorGiven a CAGR rate, solve for the ending value, beginning value or number of years, whichever you do not already know.FIFO Inventory CalculatorCost of goods sold and remaining inventory value under first-in-first-out costing.US Powerball Payout CalculatorEstimated lump-sum and annuity payout from a Powerball jackpot, after your own cash-value and tax-rate assumptions.Cross Price Elasticity CalculatorHow demand for one good responds to a price change in a different good, and whether they are substitutes or complements.Average Variable CostVariable cost per unit produced, from total variable cost and quantity.Margin Loan CalculatorCurrent loan-to-value ratio, how far a portfolio can fall before a margin call, and interest cost.28/36 Rule CalculatorMaximum recommended housing payment and total debt payment under the 28/36 mortgage affordability rule.Commercial Rent Calculator AustraliaAnnual and monthly rent from a floor area and a rate per square metre, the standard way Australian commercial leases are quoted.Prorated SalaryWhat to pay for a partial pay period, from the full annual salary and the days actually worked.Payday Loan CalculatorTrue cost of a payday loan, including the total repayment and the equivalent effective annual interest rate (APR).PVIFA (Present Value Interest Factor of Annuity)The PVIFA factor for a given rate and number of periods, plus the present value of a chosen payment.Weekly Payments CalculatorConverts a loan or bill payment amount between weekly, fortnightly, monthly, quarterly and annual frequencies.Unlevered Beta CalculatorStrips a company's financial leverage out of its observed beta, to compare risk across companies with different debt levels.Altman Z-ScoreBankruptcy-risk score for a company from five balance-sheet and income ratios.Black-Scholes option priceTheoretical price of a European call and put option.Treynor ratioReturn earned above the risk-free rate, per unit of market (beta) risk taken.EV/EBITDA multiplePrices a company against its cash operating profit, independent of capital structure.Mortgage refinance breakevenHow many months of lower payments it takes to recoup the cost of refinancing.Deferred annuity present valueWhat a stream of future payments is worth today if it does not start for several years.Futures fair value (cost of carry)Theoretical futures price implied by the spot price, financing rate and yield.Mortgage points breakevenWhether paying upfront points for a lower rate pays off before you sell or refinance.Midpoint Method Elasticity of DemandPrice elasticity of demand using the midpoint formula, which gives the same result regardless of price direction.Return on Assets CalculatorReturn on assets (ROA) from net income and total assets, the profit generated per dollar of assets held.Labour Force Participation RateShare of the working-age population that is in the labour force, employed or actively looking for work.Annual Turnover CalculatorTotal annual revenue from monthly or quarterly sales figures, the everyday business meaning of turnover.Economic Profit CalculatorProfit after subtracting both explicit costs and the opportunity cost of resources used, not just accounting costs.Continuous Compounding CalculatorFuture value using continuous compounding, A = P times e to the rt, compared against ordinary compound interest.Portfolio Beta CalculatorThe weighted-average beta of a portfolio, from each holding’s individual beta and its share of the portfolio.Profit Loss CalculatorProfit or loss and profit margin from revenue and costs.Cost Price CalculatorWorks backward from a selling price and a margin or markup percentage to find the original cost price.Occupancy Rate CalculatorOccupancy rate for a rental property, hotel or facility, from occupied units and total available units over a period.Economic Growth Rate CalculatorWorks out a GDP growth rate between two periods, adjusts it for inflation, and puts it on a per-person basis.Average Fixed Cost CalculatorFixed cost per unit at a given output level, plus average total cost when a variable cost per unit is supplied.Rent increaseNew rent after a percentage or fixed increase, with the extra cost per year.Anthropic Stock CalculatorWorks out what an investment in an IPO returns from the price you pay, the price move after listing and the share of your application you are actually allocated.Freelance hourly rateThe hourly rate a freelancer has to charge to reach a target take-home, once unbillable time, business costs and tax are accounted for.Additional funds needed (AFN)External financing a growing business needs beyond what retained earnings cover.Accrual ratioEarnings-quality check comparing the change in net operating assets to their average.Cash flow coverage ratiosWhether operating cash flow covers current liabilities and total debt.High-low methodSplits a mixed cost into fixed and variable parts from its highest and lowest activity levels.Economic Order Quantity (EOQ)Order size that minimises combined ordering and holding costs for inventory.Herfindahl-Hirschman Index (HHI)Market concentration measured from the sum of squared market shares of each firm.Cobb-Douglas Production FunctionTotal output from labour and capital inputs given their productivity and output elasticities.Covered Interest Rate ParityNo-arbitrage forward exchange rate implied by the interest rate gap between two currencies.Put-call parityChecks or solves the no-arbitrage relationship between a call, a put and the underlying.Optimal hedge ratioShare of a spot position to cover with futures to minimise portfolio variance.Implied forward rateThe interest rate implied for a future period by two spot rates of different maturities.Credit spread (bond)The extra yield a corporate bond pays over a government bond of the same maturity.Jensen's alphaRisk-adjusted return a portfolio earned above what CAPM predicted.Information ratioExcess return over a benchmark per unit of tracking-error risk taken.Profitability indexValue created per dollar invested, for ranking or screening projects.Sinking fund paymentThe regular deposit needed to reach a target sum by a future date.Holding period returnTotal return from an investment, combining price change and income received.Actual cash value (ACV)What an insurer would pay for an item today, after wear and depreciation.ADR & RevPAR (hotel revenue)Average daily rate and revenue per available room for a lodging property.Bank reconciliationReconciles your cash book balance against the bank statement balance.Customer acquisition cost (CAC)What it costs, on average, to win one new customer, and how fast that cost is repaid.Customer churn & retention rateShare of customers lost over a period, and the flip side: how many you kept.GMROI (gross margin return on investment)How many dollars of gross profit each dollar tied up in inventory returns.Direct material price varianceWhether materials cost more or less than the standard (budgeted) rate.ARM (adjustable-rate) mortgagePayment during the fixed period, and the worst-case payment once the rate can adjust.Bond current yieldThe income return a bond offers at its present market price, ignoring capital gain or loss.Return on capital employed (ROCE)Operating profit generated per dollar of capital tied up in the business.Operating marginWhat share of revenue is left as operating profit, after cost of sales and running costs.SaaS customer lifetime value (LTV)What an average subscriber is worth over their time, weighed against acquisition cost.Margin CalculatorGross margin percentage from unit cost and selling price, with markup and profit shown alongside.Net Profit MarginNet profit margin from revenue and net income, the share of revenue left after every expense.

Health

Body composition, energy needs, training load and cycle tracking, using the standard published clinical and sports-science formulas.

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Body mass index (BMI)Weight relative to height, with the WHO category.BMR: basal metabolic rateEnergy burned at complete rest (Mifflin-St Jeor).TDEE: daily calorie needsBMR scaled by how active you are.Weight change timelineHow long a given calorie gap takes to shift a target.Body fat percentage (US Navy)Tape-measure estimate of body composition.Ideal body weightFour classic clinical formulas side by side.Macronutrient splitGrams of protein, carbs and fat for a calorie target.Daily water intakeBaseline fluid target adjusted for exercise and heat.Calories burned (MET)Energy cost of an activity from its metabolic equivalent.Heart rate training zonesKarvonen zones from resting and maximum heart rate.VO₂ max (Cooper test)Aerobic fitness from a 12-minute run.One-rep maxStrength ceiling estimated from a submaximal set.Running pace & finish timeConverts between pace, speed and race time.Pregnancy due dateEstimated delivery date from the last period (Naegele’s rule).Body surface areaUsed for drug dosing and cardiac index.Waist-to-hip & waist-to-heightFat distribution measures that track health risk.Ovulation & fertile windowLikely fertile days across a cycle.Sleep cycle timingWake times that fall between 90-minute sleep cycles.Weight loss percentageWhat a starting weight and a current weight work out to as a percentage change.IVF due dateEstimated delivery date from an embryo transfer date, for Day 3 or Day 5 transfers.Body Shape CalculatorClassifies body shape, hourglass, pear, apple, rectangle or triangle, from bust, waist and hip.Standard Drink CalculatorNumber of standard drinks in a beverage from its volume and ABV, by country.eGFR (CKD-EPI 2021)Estimated kidney filtration rate from serum creatinine, age and sex, CKD-EPI 2021 equation.CHA₂DS₂-VASc ScoreStroke-risk score for atrial fibrillation: heart failure, hypertension, age, diabetes, stroke history.Stroke volumeBlood pumped by the left ventricle in a single heartbeat, from end-diastolic and end-systolic volume.BBT (Basal Body Temperature)Finds the sustained temperature rise that typically follows ovulation in a BBT chart.Face ShapeClassifies face shape, oval, round, square, heart, diamond or oblong, from four measurements.Time to sunburnHow long unprotected skin takes to burn at a given UV index and Fitzpatrick skin type, with sunscreen SPF applied.EER: estimated energy requirementDaily energy need from age, sex, weight, height and activity level, using the published adult EER equations.Gestational age and corrected ageCurrent gestational age in weeks and days during pregnancy, or a premature baby corrected age.Anion gapUnmeasured ions in the blood, a first step in narrowing the cause of a metabolic acidosis.Corrected calcium for albuminAdjusts a total calcium reading for a low albumin level, using the Payne formula.Blood alcohol content (Widmark formula)Rough estimate of blood alcohol content from drinks consumed, body weight and time elapsed.Estimated average glucose from A1CConverts an HbA1c percentage into an average blood glucose reading (ADAG study formula).Corrected QT interval (QTc)Heart-rate-adjusted QT interval from an ECG reading, using the Bazett and Fridericia formulas.Creatinine clearance (Cockcroft-Gault)Estimated kidney filtration rate from age, weight and serum creatinine.Lean body mass (Boer formula)Fat-free body mass estimated from height and weight.Mean arterial pressure (MAP)Average pressure driving blood flow through the body over one heartbeat cycle.Total body water (Watson formula)Estimated volume of water in the body from age, height and weight.Fat-free mass index (FFMI)Muscularity measure that adjusts fat-free mass for height, comparable across body sizes.Smoking pack-yearsCumulative smoking exposure used in clinical risk screening.LDL cholesterol (Friedewald equation)Estimated LDL cholesterol from a standard lipid panel.Total cholesterol to HDL ratioA single number summarizing cardiovascular risk from a lipid panel.Daily protein intakeProtein target range based on body weight and activity level.Daily fiber intake targetRecommended dietary fiber based on total calorie intake.A Body Shape Index (ABSI)Waist circumference adjusted for height and BMI, an alternative to the waist-to-height ratio.Relative fat mass (RFM)Body fat percentage estimated from height and waist circumference (Woolcott-Bernstein).Shock indexHeart rate divided by systolic blood pressure, a quick marker of circulatory stress.Rate pressure productHeart rate times systolic blood pressure, an index of how hard the heart is working.HOMA-IR (insulin resistance)Estimated insulin resistance from fasting glucose and fasting insulin levels.hCG Doubling TimeEstimates how quickly hCG levels are doubling from two blood test readings and the days between them.Urine output rateUrine output per kilogram of body weight per hour, against the commonly cited oliguria threshold.ACR TI-RADS ScoreAdds up the published ACR TI-RADS points for a thyroid nodule on ultrasound: composition, echogenicity, shape, margin and echogenic foci.Max Heart Rate CalculatorEstimated maximum heart rate from age, using the classic 220 minus age rule and the Tanaka formula.Weight Gain CalculatorDaily calorie target for a chosen weekly weight-gain rate, from TDEE and a calorie surplus.Drops Per Minute CalculatorIV infusion flow rate in drops per minute from the volume, drop factor and infusion time.GCS CalculatorGlasgow Coma Scale total score from eye-opening, verbal and motor response, for professional clinical assessment.IQ Score Ranges CalculatorWhich published classification band an IQ score falls into, using the standard Wechsler-scale ranges.Blood sugar converterConverts blood glucose readings between mg/dL and mmol/L, in either direction.Incidence Rate CalculatorThe rate of new cases per unit of person-time at risk, the standard epidemiological measure.Calculated serum osmolalityEstimates blood osmolality from a basic metabolic panel, plus the osmolal gap.Corrected sodium for hyperglycemiaAdjusts a measured sodium reading for high blood glucose, using the Katz and Hillier formulas.Delta ratio (delta gap)Compares the rise in anion gap to the fall in bicarbonate, to spot a mixed acid-base disorder.BUN-to-creatinine ratioCompares blood urea nitrogen to creatinine, used to help distinguish causes of kidney injury.AST-to-ALT ratio (De Ritis ratio)Compares two liver enzymes, sometimes used to point toward a pattern of liver injury.Albumin-to-globulin ratioSplits total blood protein into albumin and globulin and compares the two.Transferrin saturation (TSAT)The share of iron-carrying protein that is actually loaded with iron.Mentzer indexScreens a routine blood count for thalassemia trait versus iron-deficiency anemia.FEV1/FVC ratioShare of lung capacity exhaled in the first second of a forced breath, from spirometry.Minute ventilationThe total volume of air moved in and out of the lungs in one minute.Estimated height from knee heightStanding height for a patient who cannot be measured directly (Chumlea equations).Adjusted body weightBlends actual and ideal body weight, a middle-ground figure used for larger patients.Ponderal indexA leanness measure like BMI, but using height cubed for consistency at any height.Body roundness index (BRI)Estimates body shape and visceral fat from waist and height, an alternative to BMI.Osteoporosis risk score (OST index)A quick screening score from age and weight, flagging who might need bone density testing.Pregnancy weight gain guidelineRecommended weight gain for a singleton pregnancy, by pre-pregnancy BMI (IOM guidelines).Gestational age from crown-rump lengthDates an early pregnancy from a first-trimester ultrasound measurement.Fundal height gestational age (McDonald’s rule)Between 20 and 36 weeks, fundal height in centimetres roughly tracks gestational age.Glycemic loadCombines a food’s glycemic index with the actual carbohydrate in a serving.Net carbsCarbohydrate grams likely to affect blood sugar, after subtracting fibre and sugar alcohols.PF Ratio CalculatorPaO2/FiO2 ratio for lung oxygenation, with the standard Berlin ARDS bands shown for information only.Weight Loss by Date CalculatorWeekly weight-loss rate and daily calorie deficit needed to reach a goal weight by a chosen date.Salt to sodium conversionConverts salt to sodium content, or sodium back to an equivalent salt amount, using the fixed weight of NaCl.Bladder Volume CalculatorEstimated bladder capacity from age, using the standard paediatric formula, with adult reference ranges for comparison.DASI Score CalculatorDuke Activity Status Index score from 12 activity questions, with the estimated peak VO2 and METs.ECG Heart Rate CalculatorEstimates heart rate in beats per minute from the R-R interval measured on an ECG strip, for informational use.Mid-parental height predictionPredicted adult height for a child from both parents heights (Tanner method).Drug elimination by half-lifeFraction of a substance remaining or cleared after a given time, from its half-life.Predicted vital capacityExpected lung vital capacity for a healthy adult, from height, age and sex.Free water deficitEstimated water needed to correct a high serum sodium (hypernatraemia).Urine anion gapUrinary electrolyte gap that helps distinguish causes of a normal anion-gap metabolic acidosis.Fractional excretion of sodium (FeNa)Compares urine and plasma sodium and creatinine to help classify acute kidney injury.Urine protein-to-creatinine ratioEstimates 24-hour urinary protein loss from a single spot urine sample.MCH & MCHC (red cell indices)Average haemoglobin content and concentration per red blood cell, from a full blood count.Absolute neutrophil count (ANC)Total mature and immature neutrophils in circulation, used to gauge infection risk.PSA densityPSA level adjusted for prostate size, used alongside other tests to gauge cancer risk.RMR from lean mass (Katch-McArdle)Resting metabolic rate estimated from lean body mass rather than total weight.PaO₂/FiO₂ ratio (Horowitz index)Oxygenation index used to gauge the severity of acute respiratory failure.Alveolar-arterial (A-a) gradientGap between calculated and measured arterial oxygen, a clue to the cause of hypoxaemia.Bolton tooth-size ratioCompares upper and lower tooth widths to flag a size mismatch before orthodontic treatment.Amplitude of accommodation (Hofstetter)Expected eye-focusing range for a given age, and the approximate near point for reading.Number needed to treat (NNT)How many patients must be treated to prevent one additional bad outcome, from two event rates.Vaccine efficacyPercentage reduction in disease risk among a vaccinated group versus an unvaccinated group.Calories per Meal CalculatorSplits a daily calorie target evenly across a chosen number of meals.Stationary Bike Calories BurnedCalories burned on a stationary bike from body weight, session length and riding intensity.Tidal Volume CalculatorWorks out the volume of a single normal breath from minute ventilation and breathing rate.Ankle-brachial index (ABI)Peripheral artery disease screening ratio of ankle to arm blood pressure.Left ventricular ejection fractionPercentage of blood pumped out of the left ventricle with each heartbeat.Cardiac output & cardiac indexBlood pumped by the heart each minute, scaled to body size.Cerebral perfusion pressure (CPP)Net pressure driving blood flow to the brain, from blood pressure and intracranial pressure.Lung-protective tidal volume (ARDSnet)Low tidal volume ventilation target from predicted body weight and height.Physiologic dead space (Bohr equation)Share of each breath that does not take part in gas exchange.Alcohol units (UK)UK standard units of pure alcohol in a drink, from volume and strength.Reticulocyte production index (RPI)Corrects a reticulocyte percentage for anaemia severity and cell maturation time.Breast Milk Intake (mL per kg) CalculatorApproximate daily breast milk volume for a breastfed baby, from weight, age and feeds per day.Triglycerides to HDL Ratio CalculatorTriglycerides to HDL cholesterol ratio from a lipid panel, a commonly cited cardiovascular risk marker.Skinfold Body Fat Calculator (Jackson-Pollock 3-Site)Body fat percentage from three caliper skinfold measurements, age and sex, using the Jackson-Pollock 3-site equation.Contact Lens Vertex CalculatorConverts a spectacle lens prescription to the equivalent contact lens power using the vertex distance correction.Ultrasound Volume CalculatorEstimates the volume of an organ, cyst or mass from three ultrasound measurements, using the ellipsoid formula.IV Drip Rate CalculatorWorks out an IV infusion drip rate in drops per minute from the volume, time and giving-set drop factor.Albumin-to-creatinine ratio (ACR)Urine albumin relative to creatinine, a standard kidney-damage screening test.FIB-4 index (liver fibrosis)Screens for advanced liver fibrosis risk from age plus a routine liver panel and platelet count.Transtubular potassium gradient (TTKG)Estimates how well the kidney is handling potassium from paired urine and serum readings.Urea reduction ratio (URR)Percentage drop in blood urea over one haemodialysis session, a dialysis-adequacy check.Winters’ formula (expected pCO₂)Checks whether respiratory compensation for a metabolic acidosis looks appropriate.Neutrophil-to-lymphocyte ratio (NLR)A simple inflammation marker calculated from a routine blood differential.Caffeine remaining in the bodyEstimates caffeine left in your system over time using first-order elimination kinetics.Karvonen target heart rateTarget heart rate training zone from heart rate reserve, using the Karvonen formula.Body frame sizeClassifies frame size as small, medium or large from the height-to-wrist-circumference ratio.IQ percentileWhere an IQ score ranks against the population, from the normal distribution.Blood glucose unit converterConverts blood glucose readings between mmol/L and mg/dL.Adjusted age for premature babiesCorrects a premature baby’s age for weeks born early, for milestone tracking.DIY hand sanitizer recipe (WHO formula)Scales the WHO alcohol-based handrub formulations to any batch size.Safe noise exposure timeMaximum daily exposure time allowed at a given noise level, NIOSH or OSHA rules.Added sugar daily limitCompares a day’s added sugar against the AHA recommended maximum.Sleep debt trackerCumulative sleep shortfall over several nights against a target amount of sleep.Next blood donation eligibility dateEarliest date you can donate again, from your last donation and the donation type.Estimated conception dateBack-calculates a likely conception date from a due date or the start of the last period.Child blood type probabilityPossible ABO and Rh blood types of a child from both parents, classic Mendelian genetics.Baby formula daily intakeApproximate daily formula volume for a bottle-fed baby, from weight and age.US standard alcoholic drinksNumber of US standard drinks (14 g pure alcohol each) in a beverage, from volume and ABV.Baby eye color probabilityLikely eye colors for a baby from both parents’ eye colors, using a simplified genetic model.Breastfeeding extra calorie needsExtra daily calories needed while exclusively breastfeeding, on top of your baseline TDEE.Vitamin mcg to IU converterConverts vitamin A or vitamin D between micrograms (mcg) and International Units (IU).Cholesterol unit converterConverts total cholesterol, HDL, LDL or triglycerides between mg/dL and mmol/L.Calorie deficit targetDaily calorie target for a chosen weekly weight-loss rate, from TDEE.Peptide reconstitution & dose volumeMixing concentration after reconstituting a peptide vial, and draw volume for a target dose.TDEE calculatorTotal daily energy expenditure from a simple three-level activity scale.BMI calculator for womenBody mass index for women, with the WHO healthy-weight range for her height.Maintenance calories calculatorThe daily calorie level that keeps weight stable, as a number and a realistic range.Height calculatorConverts height between centimetres, metres and feet/inches.

Maths

Percentages, fractions, algebra, number theory and trigonometry, with the working shown alongside every answer rather than the result on its own.

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PercentageThe three everyday percentage questions in one place.Percentage change & differenceIncrease, decrease and the symmetric difference.Fraction arithmeticAdd, subtract, multiply or divide two fractions and simplify.Decimal ↔ fractionClosest fraction to a decimal, at a chosen precision.GCD & LCMGreatest common divisor and lowest common multiple.Quadratic equationRoots, vertex and discriminant of ax² + bx + c.Ratio & proportionSolves a : b = c : d for the missing term.Exponents & rootsPowers, nth roots and scientific notation of the result.LogarithmLog in any base, plus the natural and common logs.Scientific notationConverts between plain numbers and a × 10ⁿ.Prime check & factorisationTests primality and lists the prime factors.Permutations & combinationsOrdered and unordered selections from a set.Number base converterBinary, octal, decimal, hex and any base to 36.Roman numeral converterArabic to Roman and back, 1 to 3999.Rounding & significant figuresRound to decimals, significant figures or a nearest step.Trigonometry: solve a triangleSine and cosine rules from two sides and the included angle.Trigonometric functionssin, cos, tan and their inverses for one angle.Modulo & integer divisionQuotient, remainder and the true mathematical modulo.Random number generatorDraws numbers from a range: press recalculate for a new set.Arc LengthArc length of a circle from its radius and central angle, in degrees or radians.CuboidVolume, surface area, individual face areas and space diagonal of a cuboid from its three edge lengths.Power of 22 raised to any exponent, with a reference table of powers of 2 from 2⁰ to 2²⁰.Inverse Trigonometry (Theta)Solves backwards from a known sine, cosine or tangent ratio to the angle theta.Lowest Common Denominator CalculatorFinds the lowest common denominator of two or more fractions and rewrites each one over it.Perfect Square CalculatorChecks whether a number is a perfect square, and shows the nearest perfect squares below and above it.Fraction to Percentage CalculatorConverts a fraction to a percentage, or a percentage back to a simplified fraction.Angle of depressionThe angle below the horizontal from an elevated point down to a target, from height and horizontal distance.Percentage DecreaseNew value after a percentage decrease, or the percentage decrease between two values.Fraction to DecimalConverts a fraction to its decimal expansion, marking any repeating block clearly.Exponential FunctionEvaluates y = a × bˣ at a chosen x, with the underlying growth or decay rate.XOR CalculatorBitwise XOR of two whole numbers, with AND, OR and NOT shown alongside for comparison.Square Root CalculatorPrincipal square root of a number, whether it is a perfect square, and the nearest ones either side.Exponential GrowthProjects a value forward under a fixed percentage growth rate per period, from a starting value and number of periods.Arctan (Inverse Tangent)The angle, in degrees and radians, whose tangent equals the value you enter.Pascal's TriangleGenerates any row of Pascal's triangle as binomial coefficients, with the surrounding rows shown for context.Percentage Difference Between Two NumbersThe symmetric percentage difference between two numbers, using their average as the base, distinct from a directional percentage increase or decrease.Polar Form of a Complex NumberConverts a complex number between rectangular (a + bi) form and polar (r∠θ) form, in either direction.Similar Triangles CalculatorScale factor and missing side lengths between two similar triangles from one matching pair of sides.Factoring CalculatorFactors a quadratic trinomial ax² + bx + c into (x − r1)(x − r2) form using its roots.Simplifying Fractions CalculatorReduces a fraction to its simplest form and shows the decimal and mixed-number equivalents.Divisor CalculatorLists every divisor of a whole number, with the count and sum of divisors.Long Division CalculatorShows the full step-by-step working for long division: bring down each digit, divide, subtract, repeat.Greater Than or Less Than CalculatorCompares two numbers and shows the correct inequality symbol: greater than, less than or equal to.Million in Numbers CalculatorExpands a figure written in thousands, millions, billions or trillions into its full digit form.Power of 1010 raised to any exponent, with a reference table of powers of 10 from 10⁰ to 10¹⁰.Matrix determinant (2×2 or 3×3)Determinant of a 2×2 or 3×3 matrix from its entries.2×2 matrix inverseInverse of a 2×2 matrix using the adjugate formula.2×2 matrix operationsAdd, subtract or multiply two 2×2 matrices, and scale one by a constant.Vector dot productScalar dot product of two 3D vectors, and the angle between them.Vector cross productThe perpendicular vector from two 3D vectors, and the area of the parallelogram they span.Vector magnitude & unit vectorLength of a 3D vector and the unit vector pointing the same way.Arithmetic sequenceThe nth term and the sum of the first n terms of an arithmetic sequence.Geometric sequenceThe nth term and the sum of a geometric sequence, plus the infinite sum where it converges.Complex number arithmeticAdd, subtract, multiply or divide two complex numbers, plus modulus and argument.Synthetic divisionDivides a polynomial by (x − r) and returns the quotient and remainder.Equation of a lineSlope-intercept, point-slope and standard form of the line through two points.Distance & midpoint between two points (3D)Straight-line distance and midpoint between two points in 3D space (set z = 0 for 2D).Law of sines (solve a triangle)Finds the remaining sides and angles from two angles and one side.Arithmetic in standard formAdd, subtract, multiply or divide two numbers written as a × 10ⁿ.Binomial expansionExpands (x + y)ⁿ term by term using the binomial theorem.Distance from a point to a linePerpendicular distance from a point to a line given in general form.Geometric & harmonic meanThe geometric mean and the harmonic mean of a list of positive numbers.Golden ratioSplits a length into golden-ratio proportions, or scales a rectangle side by φ.Point-Slope Form of a LineWrites the equation of a line in point-slope form from one point and the slope, and converts it to slope-intercept form.Trapezoidal RuleApproximates the area under a curve (a definite integral) from a set of x,y data points using the trapezoidal rule.Arcsin (Inverse Sine)The angle, in degrees and radians, whose sine equals the value you enter.Cubic Metres to Tonnes ConverterConvert cubic metres to tonnes and back, using an editable density for the material involved.Logarithm Laws CalculatorDemonstrates the product, quotient and power laws of logarithms on two numbers you choose.Arccos (Inverse Cosine)The angle, in degrees and radians, whose cosine equals the value you enter.Sum of Series CalculatorThe sum of the first n terms of an arithmetic or geometric series, with the nth term shown too.Decimal to Percentage CalculatorConverts a decimal to a percentage, or a percentage back to a decimal, by multiplying or dividing by 100.Vector AdditionAdds two 2D or 3D vectors component by component and gives the resultant vector and its magnitude.Point of IntersectionWhere two straight lines cross, from their slope-intercept equations, with parallel and identical lines handled.Sine, Cosine & TangentSine, cosine and tangent of an angle you enter, in degrees or radians.Engineering NotationConverts a number to engineering notation, with a multiple-of-3 exponent and SI prefix.Constant of Proportionality CalculatorFinds k in y = kx from one x-y pair, with an optional second pair to check the relationship is genuinely proportional.Antilog CalculatorFinds the antilogarithm of a value, the number a log of that size came from, in base 10 or base e.Ambiguous Case (SSA Triangle)Works out whether an angle and two sides in the SSA arrangement give zero, one or two possible triangles.Ratio simplifierReduces a ratio of two or more numbers to its simplest whole-number form.Eigenvector CalculatorEigenvalues and eigenvectors of a 2×2 matrix, from its four entries.Partial fraction decomposition (2 factors)Splits (ax+b)/((x−p)(x−q)) into simple fractions, including the repeated-root case.System of two linear equationsSolves a₁x+b₁y=c₁ and a₂x+b₂y=c₂ for x and y.Intersection of a circle and a lineWhere a line y = mx + c crosses a circle centred at (h, k).Matrix trace & transpose (2×2 or 3×3)Sum of the diagonal, and the matrix flipped over its diagonal.Hyperbolic functionssinh, cosh and tanh of a value, and their inverses.Circle equation: general to standard formConverts x²+y²+Dx+Ey+F=0 into centre-radius form.Absolute value equationSolves |ax + b| = c for x.Consecutive integers from a sumFinds n evenly-spaced integers (consecutive, even or odd) that add to a target sum.Divisibility testChecks which numbers from 2 to 12 divide a whole number evenly.Digital rootRepeatedly sums the digits of a number until one digit remains.Cubic equationReal roots of ax³ + bx² + cx + d = 0 via Cardano’s method.Eigenvalues of a 2×2 matrixThe two eigenvalues (real or complex) of [[a,b],[c,d]] from the characteristic polynomial.Solve a·bˣ = c for xUses logarithms to isolate x in an exponential equation.Rationalize a denominatorRemoves a square root from the denominator of a/(b + c√n) using the conjugate.Pythagorean triple generatorBuilds a right-triangle integer triple from two generator numbers (Euclid’s formula).Clock hand angleThe angle between the hour and minute hands at a given time.Reference & coterminal angleReduces any angle to its 0–360° coterminal angle, quadrant and reference angle.Round to the nearest fractionRounds a decimal to the nearest 1/2, 1/4, 1/8, 1/16 or any denominator you choose.Percent errorHow far a measured or estimated value is from the accepted true value.Set operationsUnion, intersection and differences of two sets of numbers.Alphabet to Numbers CalculatorConvert letters to their A1Z26 position numbers, or numbers back to letters.Perfect Cube CalculatorChecks whether a number is a perfect cube and shows the nearest perfect cubes below and above it.Ordering Decimals CalculatorSorts a list of decimal numbers into ascending or descending order.Cross Multiply Fractions CalculatorSolves a proportion a/b = c/d for the one missing value using cross-multiplication.Linear Equation SolverSolves a simple linear equation ax + b = c for x, with guards for a zero coefficient.Doubling TimeHow long it takes a quantity growing at a fixed percentage rate to double, by the exact formula and the Rule of 72.Completing the Square CalculatorRewrites ax² + bx + c as a(x − h)² + k, showing the completing-the-square steps.Matrix Rank CalculatorRank of a 2×2 or 3×3 matrix by Gaussian elimination, the number of linearly independent rows.Common Multiples CalculatorLists the first several common multiples shared by a set of numbers, built from their lowest common multiple.Number to Words ConverterTurns a number written in words like "8 billion" into a full numeral, or a numeral back into words.Triangle Number CalculatorThe nth triangular number, the sum of 1 to n, or checks whether a given number is one.Polygon area from vertices (shoelace formula)Area, perimeter and centroid of a simple polygon from its ordered vertices.Triangle incenter & inradiusIncenter coordinates and inscribed-circle radius from a triangle’s three vertices.Perfect, abundant & deficient number checkClassifies a whole number by comparing it to the sum of its own proper divisors.Amicable numbers checkTests whether two numbers form an amicable pair: each is the sum of the other’s divisors.Continued fraction expansionExpands a fraction p/q into continued-fraction terms and lists its convergents.Linear Diophantine equation (ax + by = c)Finds all integer solutions to ax + by = c using the extended Euclidean algorithm.System of three linear equations (Cramer’s rule)Solves a 3×3 system of linear equations using determinants.Vector projectionProjects vector a onto vector b in 3D (set z = 0 for 2D vectors).Distance from a point to a planePerpendicular distance from a point to a plane given as ax + by + cz + d = 0.Chinese remainder theorem (two congruences)Finds x satisfying x≡a₁ (mod n₁) and x≡a₂ (mod n₂), including non-coprime moduli.Modular multiplicative inverseFinds x such that a·x ≡ 1 (mod n), using the extended Euclidean algorithm.nth roots of a complex numberAll n complex roots of a+bi using De Moivre’s theorem, in polar and rectangular form.Multiplication CalculatorMultiplies any two numbers and shows the result, along with a small times-table around it.Combine Percentage ChangesCorrectly combines two successive percentage changes, such as two discounts or two price rises, without wrongly adding them.Equivalent Fractions CalculatorLists fractions equal in value to the one you enter, or finds the equivalent at a target denominator.Adjugate (Adjoint) MatrixThe adjugate of a 2×2 matrix, shown as its own labelled result, alongside the determinant and inverse.Bit Shift CalculatorShifts an integer left or right by a chosen number of bits, showing the result in decimal and binary.Percentage Points CalculatorThe percentage point difference between two percentages, alongside the separate percentage change figure.Cos 2 Theta CalculatorValue of cos(2θ) for any angle, using the double angle identity, with the intermediate cos(θ) and sin(θ) shown.Fibonacci sequenceThe nth Fibonacci number, the sequence around it and the sum so far.Egyptian fraction decompositionSplits a fraction into a sum of distinct unit fractions using the greedy algorithm.Linear interpolationEstimates a missing y (or x) on the straight line through two known points.Modular exponentiationComputes baseᵉˣᵖ mod m efficiently using square-and-multiply.Luhn algorithm (checksum)Validates a number sequence or computes the check digit that makes it valid.Manhattan (taxicab) distanceGrid-style distance between two points, moving only along axes.Euler's Number (e) CalculatorComputes e raised to any power, or the natural log of a number, using Euler's number e = 2.718281828.Sort Numbers CalculatorPuts a list of numbers in order from smallest to largest, or largest to smallest.Bitwise CalculatorRuns AND, OR, XOR or NOT on two integers, showing the result in both decimal and binary.Cholesky Decomposition CalculatorDecomposes a 3×3 symmetric positive-definite matrix A into L·Lᵀ, where L is lower triangular.Null space & rank of a matrixRank, nullity and a basis for the null space of a 2×2 or 3×3 matrix.Standard calculatorA plain calculator for everyday sums, with brackets, powers, roots and the order of operations shown as it works.Matrix multiplication costCompares the scalar multiplications needed by the schoolbook method, Strassen recursion and the AlphaEvolve 4x4 algorithm for an n by n product.Equal distances in a gridCounts the pairs of lattice points sitting at exactly the same distance apart, the quantity the Erdos unit distance problem asks about.Factorial divisibilityTests whether a! times b! divides n! times (a+b-n)!, the divisibility behind Erdos problem 728, using Legendre prime exponents.Bin packingPacks a list of item sizes into fixed-capacity bins by first fit and first fit decreasing, and compares both against the unavoidable minimum.Sorting comparisonsHow many comparisons sorting n items takes, from the information-theoretic floor to what merge sort and insertion sort actually spend.Cap set growth rateTurns a cap set found in one dimension into the growth rate per dimension and the size it implies in higher dimensions by the product construction.Ramsey number boundsThe Erdos-Szekeres upper bound on R(s,t), the probabilistic lower bound on the diagonal case, and how many colourings a brute-force search would face.Minimum overlap of a splitScores a split of the first 2n whole numbers into two halves by its worst shifted overlap, the quantity Erdos asked to minimise.Collatz conjecture (3n+1)Steps to reach 1 by halving even numbers and applying 3n + 1 to odd ones.Cosine similarityAngular similarity between two vectors, from −1 (opposite) to 1 (same direction).Descartes' rule of signsMaximum possible positive and negative real roots of a polynomial, from its sign changes.Sum of digitsAdds up the individual digits of a whole number in one pass (not repeated to a single digit).Order of magnitudeThe power of ten a number sits on, used to compare sizes at a glance.Unit rateSimplifies a ratio of two quantities to a rate per single unit of the second quantity.Golden rectangleFinds the sides, diagonal and area of a rectangle whose side ratio equals the golden ratio.Magic squareFinds the magic constant of an n×n magic square and builds it for odd n via the Siamese method.Discrete convolutionConvolves two finite number sequences to produce their discrete convolution sequence.Two's complementConverts a signed decimal integer to its binary two’s-complement form at a chosen bit width.Harmonic numberSums the reciprocals of the first n positive integers to give the nth harmonic number.Gamma functionEvaluates the gamma function Γ(x) for any real x, extending the factorial to non-integers.Error functionComputes the Gauss error function erf(x) and its complement erfc(x) for a given x.Involute functionFinds the involute of a pressure angle, used in gear-tooth geometry: φ = tan(α) − α.Absolute value inequalitiesSolves |ax + b| compared to c (<, ≤, >, ≥) and shows the solution in interval notation.Euler's formula for polyhedraFinds the missing vertex, edge or face count of a convex polyhedron from V − E + F = 2.Cyclomatic complexityComplexity of a control-flow graph from its edge, node and connected-component counts.Bilinear interpolationEstimates a value at a point inside a rectangular grid from the four surrounding known values.Percentage IncreaseNew value after a percentage increase, or the percentage increase between two values.Volume of Common ShapesVolume and surface area of a cube, box, sphere, cylinder or cone from its dimensions.AverageMean, sum and count for a list of numbers.TrigonometrySolves a right-angled triangle: the missing sides and angle from one angle and one known side.Fraction CalculatorAdd, subtract, multiply or divide two fractions or mixed numbers, simplified automatically.Gradient (Slope) of a LineGradient between two coordinate points, plus the equation of the line through them.SUVAT equations solverSolve any of the five SUVAT equations of motion for the two unknowns, given the other three.Midpoint between two pointsThe point exactly halfway between two coordinates.Hypotenuse from two legsThe hypotenuse of a right triangle from its two shorter sides.X out of Y as a percentageTurns any "X out of Y" ratio, such as 32 out of 40, into a percentage.

Statistics

Averages, spread, distributions, confidence intervals and correlation for data sets you paste straight in, with the formula shown every time.

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Descriptive statisticsMean, median, mode, spread and quartiles for a data set.Weighted averageAverage where each value carries its own weight.Z-score & percentileHow far a value sits from the mean, in standard deviations.Normal distribution probabilityArea under the bell curve between two points.Confidence interval for a meanMargin of error around a sample average.Required sample sizeHow many responses a survey needs.Correlation & linear regressionPearson r and the line of best fit for paired data.Binomial probabilityChance of exactly k successes in n independent trials.Probability of eventsCombines two event probabilities: and, or, neither.Odds ↔ probabilityConverts between fractional odds, decimal odds and percent.GPA / weighted gradeGrade point average across units with credit weights.Grade needed on the finalWhat the last assessment must score to hit a target.Interquartile Range (IQR)Q1, Q3 and the interquartile range for a list of numbers.Roll a D20Rolls one or more dice of a chosen size and gives the probability of the result you asked for.Binomial DistributionFull binomial probability distribution: probability of every outcome, mean, variance, standard deviation and shape.T-testOne or two-sample t-test with the t-statistic converted to a p-value and a significance verdict.Relative frequencyEach category's share of the total, and the running cumulative share, from a list of raw counts.Ascending Order CalculatorSorts a list of numbers into ascending order, with descending order and basic stats shown too.Average Percentage CalculatorSimple and sample-size-weighted average of several percentages, and why they can differ.Letter Grade Average CalculatorAverages several letter grades by converting each to a 4.0 grade-point value, then back to a letter.Relative & Absolute ErrorAbsolute error and relative error, as a decimal ratio, between a measured and true value.Range of a Data SetThe minimum, maximum and range (spread between them) for a list of numbers.Poker Odds CalculatorRough win probability from your number of outs, using the standard rule of 2 and 4 approximation.Conditional probabilityP(A given B), worked from either the joint probability of both events or a joint frequency table.Pie Chart Percentages CalculatorTurns a list of category values into the percentage share and degree angle each slice needs for a pie chart.Simpson's Diversity Index CalculatorSimpson’s Diversity Index (1-D) from a list of species or category counts, plus the underlying Simpson’s Index and its reciprocal.Roulette Odds & Payout CalculatorProbability of winning a chosen roulette bet and its payout ratio, for European (single-zero) or American (double-zero) wheels.Coefficient of variationRelative variability of a data set: standard deviation as a percentage of the mean.SkewnessSample skewness: whether the data leans left or right of the mean.Poisson probabilityChance of a given number of independent events in a fixed interval, given the average rate.Geometric probabilityChance the first success happens on a given trial, for repeated independent trials.Hypergeometric probabilityChance of drawing an exact number of successes from a finite population, without replacement.Chi-square goodness of fitTests whether observed category counts match expected counts.Cohen's d (effect size)Standardised difference between two group means, in pooled standard deviations.Margin of error (proportion)Margin of error for a survey proportion at a chosen confidence level.Relative riskCompares event risk between an exposed and an unexposed (or treated and control) group.T-statistic (one or two sample)How many standard errors a sample mean is from the reference value, or from another mean.Z-test for a proportionTests a sample proportion against a hypothesised population proportion.Expected value of a discrete distributionMean and standard deviation of a discrete random variable from its outcomes and probabilities.Outlier fences (Tukey)The IQR-based cutoffs beyond which a data point counts as an outlier.Residual CalculatorResiduals (observed minus predicted) for a data set against its least-squares regression line.Inverse Normal Distribution CalculatorGiven a target percentile, the value and z-score for a normal distribution with a stated mean and standard deviation.Critical Value CalculatorThe critical t or z value for a given significance level, degrees of freedom and tail direction.P-Hat (Sample Proportion) CalculatorSample proportion p-hat from a count of successes and a sample size, the standard notation used before a margin of error or confidence interval.Normal Approximation CalculatorMean and standard deviation of the normal approximation to a binomial distribution, with the np≥5 rule checked.CovarianceHow two variables move together, in sample or population form.Standard error of the meanHow much a sample mean is expected to vary from the true population mean.F-test for equal variancesCompares the spread of two samples using the ratio of their variances.Negative binomial probabilityChance that the rth success happens on exactly the kth independent trial.Percentile rankWhat percentage of a data set falls at or below a given value.Value at a percentileFinds the data value at any percentile using linear interpolation.Mean absolute deviationThe average distance of each data point from the mean (or median).Bayes’ theoremUpdates the probability of an event given new evidence.Class width for a histogramHow wide each bin should be, from either a target class count or Sturges’ rule.Spearman’s rank correlationMeasures a monotonic relationship between two variables using their ranks, ties included.Chebyshev’s theoremMinimum share of any data set within k standard deviations of the mean, whatever its shape.Two-proportion z-testTests whether two independent samples have significantly different proportions.Geometric meanThe geometric mean of a set of positive numbers, contrasted with the ordinary arithmetic mean.DPMO CalculatorDefects per million opportunities from a defect count, units produced and opportunities per unit, the standard Six Sigma quality metric.Dice Sum ProbabilityProbability of a target sum when rolling two or more dice together, with the full sum distribution.Drop Rate CalculatorProbability of getting at least one item drop over a number of attempts, from a per-attempt drop chance.Poker Probability CalculatorProbability and odds of being dealt a chosen poker hand from a standard 52-card, 5-card deal.Percent to Letter Grade CalculatorConverts a single percentage score to a letter grade on a common 10-point scale.Implied Probability CalculatorConverts decimal, fractional or American betting odds into the implied win probability.Lottery Odds CalculatorOdds of matching every number in a lottery draw, from the total number pool and how many are drawn.Pooled standard deviationCombines two sample standard deviations into one pooled estimate for equal-variance tests.Z-test for a single meanTests a sample mean against a hypothesised mean when the population standard deviation is knownQuartile deviationHalf the interquartile range: a robust spread measure, less sensitive to outliers than the SD.Range rule of thumb for standard deviationA quick estimate of standard deviation from just the minimum and maximum of a data set.Mean & standard deviation from grouped dataEstimates the mean and standard deviation of a frequency table using class midpoints.Empirical rule (68-95-99.7)The share of normal data expected within 1, 2 and 3 standard deviations of the mean.KurtosisSample excess kurtosis: how heavy-tailed a data set is versus a normal distribution.Average Star CalculatorOverall average star rating from a breakdown of how many 1 to 5 star reviews were left.Implied Odds CalculatorWhether a drawing hand is profitable to call once likely future winnings are added to the pot.Continuity Correction CalculatorAdjusts a discrete value by ±0.5 before converting to a z-score, for approximating a discrete distribution with the normal curve.Marks Needed to Pass CalculatorMarks needed on a remaining test to reach an overall passing percentage.Roulette Odds CalculatorWin probability, payout odds and house edge for straight-up and even-money roulette bets, European or American wheel.TRIFR CalculatorTotal Recordable Injury Frequency Rate from recordable injuries and hours worked.Diagnostic test accuracy metricsSensitivity, specificity, predictive values and accuracy from a 2×2 test result table.Birthday paradox probabilityChance that at least two people in a group share the same birthday.Bonferroni correctionAdjusts the significance threshold when running many statistical tests at once.Benford's law leading-digit checkCompares a data set's leading digits against the distribution natural data follows.One-way ANOVA (F-statistic)Tests whether three or more group means differ, from the raw data in each group.Lotto Odds CalculatorOdds of matching every main number in a lottery draw, with or without a separate bonus ball pool.McNemar's testTests whether paired binary outcomes changed, using the two discordant-pair counts.Mann-Whitney U test (Wilcoxon rank-sum)Compares two independent samples for a shift in distribution, using ranks instead of means.MidrangeThe midpoint between the smallest and largest value in a data set, a quick measure of centre.Sum of squaresTotal squared deviation of each data point from the mean, the building block of variance.Confusion matrixTurns the four counts of a binary confusion matrix into accuracy, precision, recall and F1.Youden's indexCombines a test’s sensitivity and specificity into one score of diagnostic performance.Weibull distributionComputes the PDF, CDF, mean and variance of a Weibull distribution from its shape and scale.Rayleigh distributionComputes the PDF, CDF, mean and variance of a Rayleigh distribution from its scale parameter.Fisher's exact testRuns a two-tailed Fisher exact test on a 2×2 contingency table of counts.Process capability indexCalculates Cp and Cpk from specification limits, the process mean and standard deviation.Degrees of freedomWorks out degrees of freedom for a one-sample, two-sample or chi-square test.Index of qualitative variationMeasures diversity among categorical frequencies on a 0 to 1 scale using the IQV formula.Beta distributionPDF, mean and variance of a beta distribution from its two shape parameters.Monty Hall problemWin probability from staying versus switching after the host reveals losing doors.Statistical power analysisAchieved power for a given sample size, and the sample size needed for a target power.Error propagationPropagates the uncertainty of two measurements through a sum, difference, product or quotient.p-value from a test statisticConverts a z, t, chi-square or F test statistic into a p-value, for any tail direction.Test grade / score percentageScore percentage and standard letter grade from correct answers out of total questions.Coin flip probabilityFlips a virtual coin and works out the probability of a given number of heads.Grade CalculatorOverall course grade and letter grade from a list of assignment scores and their weights.Median CalculatorThe middle value of a data set, sorted, with the position(s) used shown.

Geometry

Area, perimeter, volume and surface area for flat shapes and solids, plus coordinate geometry, triangles and the constructions built on them.

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CircleArea, circumference and diameter from any one measure.Circle sector & arcA wedge of a circle: arc length, area and chord.Triangle from three sidesArea, angles and centres via Heron’s formula.Right triangle / PythagorasThird side, angles and area of a right-angled triangle.Rectangle & squareArea, perimeter and diagonal.TrapezoidArea and perimeter of a four-sided figure with parallel sides.Parallelogram & rhombusArea from base and height, or from sides and angle.EllipseArea, perimeter (Ramanujan) and eccentricity.Regular polygonArea, angles and radii of an n-sided regular shape.SphereVolume and surface area from the radius.CylinderVolume, surface area and capacity of a tube or tank.ConeVolume, slant height and surface area.Rectangular prism & cubeVolume, surface area and space diagonal of a box.PyramidVolume and surface area of a rectangular-based pyramid.Torus (ring)Volume and surface of a doughnut shape.Distance, midpoint & slopeEverything about the line between two points.Area & volume unit scalingHow area and volume change when a shape is scaled.Perimeter of a SectorPerimeter of a circle sector from its radius and central angle: two radii plus the arc.Square Pyramid VolumeVolume of a square-based pyramid from its base side and height, with slant height shown.Surface Area of a Square PyramidTotal and lateral surface area of a square-based pyramid from its base side and height.Heptagon CalculatorArea and perimeter of a regular heptagon from its side length, apothem or circumradius.Area of a KiteArea of a kite from the lengths of its two diagonals.Volume of a CubeVolume, surface area and space diagonal of a cube from its side length.Area of Semicircle CalculatorArea, perimeter and arc length of a semicircle from its radius or diameter.Volume of a HemisphereVolume and surface area of a hemisphere (half a sphere) from its radius or diameter.Dodecagon CalculatorArea and perimeter of a regular 12-sided dodecagon from its side length, apothem or circumradius.Cross-Sectional AreaArea of a slice cut across a circular, rectangular or pipe-shaped object.Vertex Form CalculatorRewrites a quadratic from standard form into vertex form a(x-h)²+k, with the vertex shown.Diameter to Radius CalculatorConverts a circle’s diameter to its radius, or a radius to its diameter, both directions.Height of a TriangleSolves for a triangle’s height from its area and base, or the height of an equilateral triangle from its side.Hexagonal PyramidVolume and surface area of a right pyramid with a regular hexagonal base, from the base edge length and height.Rectangular Pyramid VolumeVolume of a pyramid with a rectangular base, from its length, width and height.Volume of Rectangle (Rectangular Box)Volume of a rectangular box (cuboid) from its length, width and height.Diagonal of a RectangleThe diagonal length of a rectangle from its two side lengths, using the Pythagorean theorem.Trapezium Prism VolumeVolume of a prism with a trapezium cross-section, from its two parallel sides, height and prism length.Area of QuadrilateralArea of any four-sided shape from the (x,y) coordinates of its four corners, using the shoelace formula.Complementary AngleThe complement (90° minus the angle) and supplement (180° minus the angle) of a given angle.Pixel Circle GeneratorWhich grid squares to fill to draw a circle of a given pixel diameter, row by row.Area of common shapesArea of a circle, square, rectangle or triangle from one shared calculator.Length and WidthSolves for the missing side of a rectangle from its area or perimeter and one known side.Euclidean DistanceStraight-line distance between two points in 2D or 3D from their coordinates.Volume in LitresVolume in litres of a box, tank or container from its length, width and height.Surface Area to Volume RatioSurface area, volume and the resulting surface-area-to-volume ratio for a cube, sphere or cylinder.Angle Between Two VectorsAngle between two 2D or 3D vectors from their components, using the dot product.Degrees in a TriangleThe fixed 180° angle sum of any triangle, plus a mini calculator for the third angle from two known ones.Aquarium VolumeVolume of a rectangular aquarium in litres and gallons, from its length, width and height.Triangle Centroid CalculatorThe centroid of a triangle, the balance point, from the coordinates of its three vertices.30-60-90 Triangle CalculatorAll three sides and the area of a 30-60-90 right triangle from any one known side.Isosceles Right Triangle CalculatorThe sides, hypotenuse and area of a 45-45-90 isosceles right triangle from any one known side.Decagon CalculatorArea and perimeter of a regular decagon from its side length, apothem or circumradius.Truncated Cone CalculatorVolume, slant height and surface area of a truncated cone (frustum) from its two radii and height.Lateral & Surface Area of a Trapezoidal PrismLateral and total surface area of a trapezoidal prism from its cross-section and length.Isosceles Trapezium CalculatorArea, perimeter and base angles of an isosceles trapezium from its two parallel sides and equal leg length.Second Moment of Area CalculatorSecond moment of area (and polar second moment) for a rectangle, solid circle or hollow tube cross-section.Volume of a Parallelepiped CalculatorVolume of a parallelepiped from three edge vectors sharing a common vertex, using the scalar triple product.Triangular Pyramid Surface AreaTotal surface area of a regular tetrahedron (all four faces equilateral) from its edge length.Vertical Exaggeration CalculatorHow much a cross-section or map profile stretches vertical relief compared with its horizontal scale.Hollow Cylinder Volume CalculatorVolume, wall thickness and surface area of a pipe or tube from its outer and inner radius.Diameter of a Cylinder CalculatorVolume and surface area of a cylinder from its diameter and height, without converting to radius first.Pot Volume CalculatorVolume in litres of a cylindrical pot, bucket or planter from its radius or diameter and height.Degrees Decimal Minutes (DDM) ConverterConverts a coordinate between decimal degrees and degrees decimal minutes (D° M.mmm′) format.Square in a Circle CalculatorThe largest square that fits inside a circle, or the smallest circle that fits around a square.Base of a TriangleFinds the base of a triangle from its area and height, by rearranging the area formula.Height of a Cone (from Slant Height)Finds the vertical height of a cone from its base radius and slant height, using Pythagoras.Minecraft Arch GeneratorBlock-by-block column heights for a symmetric semicircular arch of a given width in Minecraft.Hexadecagon (16-Sided Shape) CalculatorArea, perimeter and interior angle of a regular 16-sided polygon (hexadecagon) from its side length.Triangle Vertices CalculatorArea and perimeter of a triangle from the (x, y) coordinates of its three vertices, using the shoelace formula.Radius of a CylinderSolve for the radius of a cylinder from its volume and height, or from its curved surface area and height.Centroid of Rectangle CalculatorCentroid (geometric centre) of a rectangle from its width and height.Triangular Prism Surface Area CalculatorSurface area and volume of a right triangular prism from its right-angle leg lengths and prism length.Slant Height CalculatorFinds the slant height of a cone or a square pyramid from its vertical height and base measurement.Latus Rectum CalculatorFinds the latus rectum of a parabola, ellipse or hyperbola from its defining parameters.Radius of Curvature CalculatorFinds the radius of a circular arc from its chord width and its height at the middle (the sagitta).Circles around a circleHow many circles of a given radius fit around a central circle while each touches it, and how much angular slack is left over.Unit circle pointCoordinates, quadrant, reference angle and sin/cos/tan for a point on the unit circle.Perimeter of common shapesPerimeter or circumference of a rectangle, square, circle, triangle or regular polygon, from one shared calculator.Triangular prismVolume and surface area of a triangular prism from its base sides and length.CircumferenceCircumference of a circle from its radius or diameter, with area shown alongside.DiameterDiameter of a circle from its radius, area or circumference.Area of a CircleArea of a circle from its radius, diameter or circumference, plus the circumference itself.Volume of a CylinderVolume of a cylinder from its radius and height, with capacity in litres.Surface Area of a CylinderTotal and curved surface area of a cylinder from its radius and height.Triangle AreaArea of a triangle from base and height, three sides, or two sides and the included angle.Pythagoras Theorem HypotenuseSolve the Pythagorean theorem for the hypotenuse, or for a missing leg.Area of TrapeziumArea of a trapezium from the two parallel sides and the height between them.HexagonArea and perimeter of a regular hexagon from its side length, across-flats or across-corners measure.Isosceles TriangleArea, perimeter and angles of an isosceles triangle from its equal sides and base.Cone VolumeVolume of a cone from its base radius and height.Scalene TriangleArea, perimeter and angles from three sides, with a check that the triangle is scalene.Minecraft Circle GeneratorBlock-by-block grid for building a circle of a given diameter in Minecraft.RadiusRadius of a circle from its diameter, circumference or area.Sector AreaArea of a circle sector from its radius and central angle, with arc length shown alongside.Surface Area of a Triangular PrismTotal surface area of a triangular prism from its base sides and length.Triangle CalculatorSolve a triangle for its area, sides and angles from three common known-value combinations.Area of a RectangleArea of a rectangle from its length and width, with perimeter and diagonal shown alongside.Sphere VolumeVolume of a sphere from its radius, with surface area and litre capacity shown alongside.Angle of a Right TriangleFind an unknown angle of a right-angled triangle from two known sides.Circumference to DiameterConvert a circle’s circumference to its diameter, or a diameter to its circumference.Rhombus AreaArea of a rhombus from its two diagonals, or from a side length and interior angle.Diameter of a CircleRadius, circumference and area of a circle worked out from its diameter.Parallelogram AreaArea of a parallelogram from base and height, or from two sides and the included angle.Distance Formula (2D & 3D Points)Straight-line distance between two coordinate points, in a plane or in 3D space.Triangular Pyramid VolumeVolume of a triangular pyramid (tetrahedron) from its base sides and height.Pentagon ShapeArea, perimeter and angles of a regular pentagon from its side length, apothem or circumradius.Equilateral TriangleArea, perimeter, height and angles of an equilateral triangle from its single side length.OctagonArea, perimeter and angles of a regular octagon from its side length, across-flats or across-corners measure.Square Metre CalculationWork out the square metreage of a room in square metres, including an L-shaped room with an alcove.Area of a SphereSurface area of a sphere from its radius, with diameter and volume shown alongside.DiagonalDiagonal length of a rectangle, square or cube from its side lengths.

Conversion

Unit converters that show the full ladder of equivalents at once, not just the one pair you asked for, across length, mass, volume and more.

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Length & distanceMetric and imperial length, from millimetres to nautical miles.Weight & massGrams, kilograms, pounds, ounces, stone and tonnes.Volume & capacityLitres, millilitres, gallons, pints, cups and cubic units.AreaSquare metres, hectares, acres and square feet.SpeedKilometres per hour, miles per hour, metres per second, knots.TimeSeconds through to centuries.Digital storageBytes, kilobytes, mebibytes and the binary versus decimal split.PressurePascals, bar, psi, atmospheres and millimetres of mercury.EnergyJoules, calories, kilowatt-hours and BTU.PowerWatts, kilowatts, horsepower and BTU per hour.AngleDegrees, radians, gradians and turns.Cooking measuresCups, spoons, millilitres and fluid ounces for the kitchen.TemperatureCelsius, Fahrenheit, Kelvin and Rankine.Fuel economyLitres per 100 km, miles per gallon and km per litre.Height & weight (imperial ↔ metric)Feet-and-inches and stone-and-pounds, both ways.Hex to RGB Colour ConverterConverts a hex colour code to its RGB values, or RGB values to a hex code, both directions.Nm to ft-lbs ConverterConverts between newton-metres and foot-pounds of torque, both directions.Minutes in a YearHow many minutes are in a year, for a common, leap or average calendar year, or a number of years.Ha to Acres (Australia)Converts hectares to acres or acres to hectares, for sizing Australian rural and farm land.Tablespoons to Grams ConverterConverts tablespoons to grams or grams to tablespoons, for a chosen ingredient, both directions.Cup to mL ConverterConverts cups to millilitres or millilitres to cups, for a US, metric or UK/Imperial cup.Cubic Meter CalculatorVolume in cubic metres of a box, room or load from its length, width and height.Scale CalculatorConverts a real-world measurement to a scaled drawing or model size, or a scale value back to real life.Binary to Text ConverterConverts binary (8-bit groups) to readable text, or text to binary, in either direction.Seconds in a Year CalculatorHow many seconds are in a year, for a common, leap or average calendar year, or a number of years.Mbps download timeHow long a download or upload takes at a given Mbps speed, or the speed needed for a target time.mg to mL ConverterConverts milligrams to millilitres or millilitres to milligrams, for water or a chosen liquid density.Density unit converterConverts a density value between g/cm3, kg/m3, kg/L, g/mL, lb/ft3 and oz/in3.Minutes to Seconds ConverterConverts minutes to seconds or seconds to minutes, both directions.Days to Years CalculatorConverts days to years or years to days, both directions, using an average calendar year.Days to Months CalculatorConverts days to months or months to days, both directions, using an average calendar month.Months to Years CalculatorConverts months to years or years to months, both directions, using the exact 12 months in a calendar year.Kms to Miles CalculatorConverts kilometres to miles or miles to kilometres, both directions, using the exact 1.609344 factor.Fahrenheit to Celsius CalculatorConverts Fahrenheit to Celsius or Celsius to Fahrenheit, both directions, including common oven temperatures.Gematria CalculatorConverts a word or phrase to its numeric value under English, Hebrew or Pythagorean gematria.Ounces to Grams ConverterConverts ounces to grams or grams to ounces, using the exact 28.3495 g factor.Light Year ConversionConverts light-years to kilometres, miles or astronomical units, both ways.Kg to Litres ConverterConverts kilograms to litres or litres to kilograms for a substance of a given density, since the two units are not directly equivalent.Zulu Time ConverterConverts a local clock time to Zulu (UTC) time from a UTC offset, with the date change flagged.m/s to km/h ConverterConverts metres per second to kilometres per hour or km/h to m/s, using the exact ×3.6 factor.Nm to M Converter (Length)Converts nanometres to metres or metres to nanometres, an exact base-10 length conversion.Milliseconds to Seconds ConverterConverts milliseconds to seconds or seconds to milliseconds, both directions.Ounces to mL ConverterConverts fluid ounces to millilitres or millilitres to fluid ounces, US or UK/Imperial.Teaspoon to mL ConverterConverts teaspoons to millilitres or millilitres to teaspoons, standard or US size.Minutes to Decimal CalculatorConverts minutes to a decimal fraction of an hour, or a decimal back to minutes.Fluid Ounces to Cups ConverterConverts fluid ounces to cups or cups to ounces, using the exact 8 fl oz = 1 cup ratio.Kilos to Stones CalculatorConverts kilograms to stones and pounds, or stones to kg, using the exact 6.35029 kg factor.Dozen ConverterConverts between dozens and individual items, using the fixed 1 dozen = 12 count.Million to Billion ConverterConverts between millions and billions, using the fixed factor of 1,000 million per billion.Cents to Dollars CalculatorConverts cents to dollars or dollars to cents using the fixed 100-cents-per-dollar relationship.Mbps to MB/sConverts network speed in megabits per second to megabytes per second, and back.Cubic Centimetres to MillilitresConverts cubic centimetres (cm3) to millilitres, using the exact 1:1 relationship between the two units.Billion to Trillion ConverterConverts between billions and trillions, using the fixed factor of 1,000 billion per trillion.Megabits to Megabytes CalculatorConverts a data amount between megabits (Mb) and megabytes (MB), the size of a file or download rather than a transfer speed.Time to Decimal CalculatorConverts a full time of hours, minutes and seconds into decimal hours, such as 2:15:00 into 2.25.Hex to Text ConverterConverts hexadecimal byte pairs to readable text, or text to hex, in either direction.Crore CalculatorConverts between the Indian numbering system (lakh, crore) and the Western system (million, billion).Weeks per Year CalculatorHow many weeks are in a year, or any chosen number of years, using both the rounded 52-week figure and the precise average.Watts to Kilowatts ConverterConverts watts to kilowatts or kilowatts to watts, using the exact ÷1,000 factor.PPM to mg/L ConverterConverts parts per million to milligrams per litre for dilute water-based solutions, where 1 ppm is approximately 1 mg/L.Kg to Newtons ConverterConverts a mass in kilograms to a weight force in newtons, or back, using gravitational acceleration.kPa to PSI Tyre Pressure ConverterConverts tyre pressure between kilopascals, PSI and bar, in either direction.Mm to Imperial ConversionConverts millimetres to inches, both as a decimal and as the nearest common fraction of an inch, for trade and engineering use.Seconds to Days ConverterConverts seconds to days, or days to seconds, using the fixed 86,400 seconds per day.Minutes to Days CalculatorConverts minutes to days, or days to minutes, using the fixed 1,440 minutes per day.mL to µL ConversionConverts millilitres to microlitres, or microlitres to millilitres, using the fixed 1,000 µL per mL, for lab and pipette work.Quart to Cups ConverterConverts US quarts to cups or cups to quarts, using the exact 1 quart = 4 cups ratio.Drops in mL ConversionConverts a volume in millilitres to a total drop count, or drops back to millilitres, using an editable drop factor.TorqueNewton-metres, foot-pounds, inch-pounds and kilogram-force metres.Concentration (ppm, ppb, %)Parts per million, parts per billion and percentage, as the same ratio expressed differently.12-hour ↔ 24-hour (military) timeClock time converted to 24-hour military format, and back.KSI to MPa ConverterConverts stress or pressure values between ksi and megapascals, in either direction.Microgram to milligram converterConverts microgram (mcg) amounts to milligrams, or milligrams to micrograms, both directions.Grams to MillilitresConverts grams to millilitres or millilitres to grams, using a density you set, not a fixed 1:1 factor.Baking Pan Size (Inches to cm) ConverterConverts a baking pan's length and width from inches to centimetres, with common pan sizes for quick reference.Weeks to Years ConverterConverts weeks to years or years to weeks, both directions, using the exact 365.25/7 average.PPM CalculatorConverts a percentage to parts per million, or ppm back to a percentage, using the fixed 1% = 10,000 ppm ratio.Mbps to Gbps ConverterConverts network speed between megabits and gigabits per second (1,000 Mbps = 1 Gbps).mL to Cups ConverterConverts millilitres to cups or cups to mL, with metric, US customary or US legal cup sizes.Grams to caloriesConverts grams of protein, carbs, fat or alcohol to calories, or calories back to grams.Seconds to Years ConverterConverts seconds to years or years to seconds, both directions, using an average calendar year.Kilobytes to Megabytes CalculatorConverts kilobytes to megabytes or back, letting you choose the binary (1024) or decimal (1000) convention.Mil to mm ConverterConvert mils (thousandths of an inch) to millimetres and back, using the fixed 0.0254 mm-per-mil definition.CC to mL conversionConvert cc to mL exactly (a 1:1 equivalence), plus equivalents in fluid ounces and tablespoons.Astronomical distance (AU, light-year, parsec)Distances across the solar system and beyond: astronomical units, light-years and parsecs.Degrees, minutes, seconds ↔ decimal degreesConverts a geographic coordinate between decimal degrees and degrees-minutes-seconds format.Mbps to GB Data TransferredHow many gigabytes move at a given Mbps speed over a chosen duration.Hours to Years ConverterConverts hours to years or years to hours, both directions, using an average calendar year.Ounces to Grains CalculatorConverts avoirdupois ounces to grains, or grains to ounces, in either direction.Joules to VoltsVoltage from energy in joules and electric charge in coulombs, since the two units need a charge value to relate.Square Inch to Square FootConverts a known area between square inches and square feet, in either direction.Hours to Seconds ConverterConverts hours to seconds or seconds to hours, both directions, using the exact 3,600 seconds per hour factor.Fuel Cost Per Km CalculatorCost of fuel for a distance or trip, from a consumption rate in L/100km and the price per litre.Mils to mm CalculatorConverts thousandths of an inch (mils, or thou) to millimetres, and back again.Cc ConverterConverts cubic centimetres to millilitres, litres or cubic inches, and back.House Square to Square Metres ConverterConverts the old real-estate "square" (100 sq ft) to square metres, or square metres back to squares.Upload CalculatorHow long a file will take to upload, from the file size and your upload speed.Billiard Table Sizes CalculatorPlaying-surface dimensions, area and rail perimeter for standard pool and snooker table sizes, converted to any unit.Pixel to Inches ConversionConverts a pixel measurement to inches, or inches to pixels, at any DPI you choose.Mg per dL to Mmol per L ConverterConverts mg/dL to mmol/L or back, for any substance, using an editable molar mass.Greek Gematria CalculatorConverts Greek letters to their traditional isopsephy numeric value, alpha through omega.Download Time CalculatorHow long a file will take to download, from the file size and your download speed.Pint to Cups CalculatorConverts pints to cups (or cups to pints) using either the US or UK imperial pint definition.Megabytes to Gigabytes CalculatorConverts megabytes to gigabytes or back, using either the decimal (1000) or binary (1024) convention.Mesh to Micron ConverterApproximate opening size in microns for a given sieve or screen mesh number, and back again.Days to Weeks CalculatorConverts any number of days to weeks, or weeks back to days, both directions.Square Feet to Square Metres ConverterConverts a known area between square feet and square metres, both directions.Upload Speed CalculatorWorks out the effective upload speed from a file size and the time an upload actually took.Kg to Gallons ConverterConverts kilograms to US or UK gallons or back, for a substance of a given density.Speed Unit ConverterConverts a speed between metres per second, kilometres per hour, miles per hour, knots and feet per second.Minutes to Decimal Hours ConverterConverts hours and minutes into decimal hours for timesheets, or a decimal figure back into hours and minutes.Square Yards CalculatorWorks out an area in square yards from length and width in feet, yards or metres, with the equivalent in square feet and square metres.Inch-Pounds to Newton-Metres ConverterConverts torque between inch-pounds, foot-pounds and newton-metres, in either direction.Millilitres ↔ grams (kitchen liquids)Converts ml to grams or grams to ml for water, milk, honey and other common liquids.Hectares to AcresConverts between hectares and acres, both directions, using the exact 2.47105 factor.Inches to CmConverts between inches and centimetres, both directions, using the exact 2.54 cm factor.Grams in a TablespoonWeight in grams of a tablespoon of a common ingredient, such as butter, sugar or flour.Pounds to KilosConverts between pounds and kilograms, both directions, using the exact 0.453592 kg factor.Minutes to HoursConverts between minutes and hours, both directions, with the result also shown as hours and minutes.Knots to Km/hConverts between knots and kilometres per hour, both directions, using the exact 1.852 factor.Hours to DaysConverts between hours and days, both directions, including the remainder as hours.Weeks to MonthsConverts between weeks and months, both directions, using an average calendar month.mcg to mgConverts between micrograms and milligrams, both directions, using the exact 1000x factor.Tablespoon to mLConverts tablespoons to mL or mL to tablespoons, for US, UK/metric or Australian sizes.

Date & time

Ages, durations, working days, deadlines and timesheets, worked out on real calendar arithmetic including leap years and weekends.

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Age calculatorExact age in years, months and days, plus the next birthday.Days between datesElapsed time between two dates, with and without weekends.Add or subtract from a dateThe date a set number of days, weeks or months away.Working daysCounts weekdays between two dates, less any holidays.Time duration arithmeticAdds and subtracts hours, minutes and seconds.Timesheet & payHours worked in a shift and what they are worth.Day of the week & week numberWhich weekday a date falls on, plus ISO week and day of year.Countdown to a dateTime remaining until a deadline or event.Unix timestamp converterEpoch seconds to a readable date and back.Months from todayThe date a set number of months before or after any starting date.Weeks CalculatorThe date a chosen number of weeks from today or before today, from any starting date.Days until New YearA countdown to the next 1 January, worked out from any starting date.Fortnights Remaining CalculatorHow many fortnights (14-day periods) are left between any two dates, worked out live from today.Date X Months Ago CalculatorThe calendar date a chosen number of months before or after a given date, handling month-end edge cases correctly.Years Ago CalculatorThe calendar date a chosen number of years before or after a given date, handling 29 February correctly.Minutes From Now CalculatorAdds a chosen number of hours and minutes to the current time to show what time it will be.Hours Until a Weekday CalculatorHours and days until the next occurrence of a chosen day of the week starts.Weeks in the Year So Far CalculatorWhole weeks that have elapsed since 1 January, for today or any reference date you choose.Pregnancy countdownDays, weeks and percentage remaining until a due date, from the due date itself or the last period.BC and AD Timeline CalculatorYears elapsed between a BC (BCE) year and an AD (CE) year, correctly accounting for there being no year zero.Days from today calculatorThe date a chosen number of days from now, or before now.How old am IYour exact age in years, months and days, worked out from your date of birth.Time Until a Clock TimeTime remaining until a target time today, such as 3:15 pm, counted from the current time.Weeks left in the yearHow many weeks remain until 31 December, worked out from today or any reference date you choose.

Physics

Mechanics, electricity, energy, optics and waves: first-principles formulas with every constant stated and every unit shown in the working.

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Ohm’s lawVoltage, current, resistance and power from any two.Resistors in series & parallelCombined resistance of up to four resistors.Voltage dividerOutput voltage across the lower resistor of a pair.Electricity running costWhat an appliance costs to run over time.Force, mass & accelerationNewton’s second law, with weight under gravity.Kinetic & potential energyEnergy of a moving or raised mass.Speed, distance & timeJourney arithmetic in metric and imperial.Acceleration & stopping distanceUniform acceleration, braking distance and reaction gap.Projectile motionRange, peak height and flight time of a launched object.Density, mass & volumeAny one of the three from the other two.Pressure from force or depthPressure under a load, and water pressure at depth.Wave speed, frequency & wavelengthRelates the three properties of any wave.Work, power & efficiencyEnergy transferred, the rate of transfer and what is lost.Momentum & impulseMomentum of a mass and the force needed to change it.Ideal gas lawPressure, volume, temperature and moles of a gas.Torque & rotational powerTurning force, and the power it delivers at a given speed.VelocityAverage velocity from displacement and time, or from initial speed, acceleration and time.Watts to ampsCurrent from power and voltage, or power from current and voltage, both ways.Heat Capacity of WaterHeat energy to warm or cool a mass of water, using water's fixed specific heat, plus heating time.Evaporation RateEstimated water evaporation rate and volume lost per day from a surface, using a standard simplified formula.G-ForceConverts acceleration to g-force, or a target g-force back to acceleration, using standard gravity.Polar Moment of InertiaPolar moment of inertia and section modulus for a solid or hollow circular cross-section.Power-to-weight ratioPower divided by weight, in watts per kilogram or horsepower per tonne, for vehicles, engines or athletes.kVA to AmpsConverts electrical load between kVA and amps for single or three-phase supply, both ways.Water DensityDensity of pure water at a given temperature, from 0°C to 100°C.Dew PointDew point temperature from air temperature and relative humidity, using the Magnus formula.Normal ForceNormal force a surface exerts on an object, on a flat surface or an incline.Air DensityDensity of air from temperature, pressure and relative humidity, using the ideal gas law.Centrifugal ForceThe apparent outward force felt in a rotating reference frame, from mass, speed and radius.Hydrostatic PressureFluid pressure at depth from fluid density and depth, gauge and absolute.Angle of IncidenceAngle of reflection and total ray deflection, from the angle of incidence.Specific Gravity CalculatorRatio of a substance's density to a reference fluid (water or air), the standard sink/float and concentration check.Water ViscosityDynamic and kinematic viscosity of pure water at a given temperature, from 0°C to 100°C.Flow RateVolumetric and mass flow rate from cross-sectional area, velocity and fluid density.Wet Bulb TemperatureWet-bulb temperature from dry-bulb air temperature and relative humidity.Net ForceThe resultant of several forces acting along one line, and the acceleration it produces.Mechanical StressStress on a material from an applied force and the cross-sectional area it acts over.Inverse square lawHow intensity of light, sound, radiation or gravity falls off with distance from a source.Conservation of massSolves for a missing mass in a closed system using total mass in equals total mass out.Refractive indexRefractive index of a medium from the speed of light in that medium.AzimuthThe compass bearing from an observer to a target point, from the latitude and longitude of both.Low Pass Filter CalculatorRC low-pass filter cutoff frequency from resistance and capacitance, or solve for the resistance or capacitance needed for a target cutoff.Capacitance CalculatorCapacitance from stored charge and voltage (C = Q/V), or solves for charge or voltage, with a pF/nF/uF/F conversion table.High Pass Filter CalculatorRC high-pass filter cutoff frequency from resistance and capacitance, or solve for the resistance or capacitance needed for a target cutoff.Section Modulus CalculatorElastic section modulus of a rectangular beam cross-section, or from a known second moment of area and distance to the extreme fibre.Reaction Time CalculatorDistance travelled during a driver’s reaction time before braking begins, from speed and reaction time.Tension CalculatorTension in a rope or cable for a hanging or vertically accelerating mass, or a single cable holding a mass at an angle.Water Vapour Pressure CalculatorSaturation vapour pressure of water at a given temperature, using the Arden Buck equation.Specific Gas Constant CalculatorSpecific gas constant of any gas from its molar mass, using the universal gas constant.Charles' Law CalculatorVolume or temperature of a gas at constant pressure, using Charles' Law.Centripetal force & circular motionForce, acceleration and period of an object moving in a circle at constant speed.Hooke's law & spring energyRestoring force and stored energy of a stretched or compressed spring.Pendulum periodSwing period of a simple pendulum for small angles.Elastic & inelastic collisionFinal velocities of two colliding masses, in a straight line.Capacitor charge & energyStored charge and energy of a capacitor at a given voltage.Inductor stored energyMagnetic energy stored in an inductor carrying current.RC circuit charge & dischargeHow a capacitor charges or discharges through a resistor over time.Carnot efficiencyMaximum possible efficiency of a heat engine between two temperatures.Linear thermal expansionHow much a material lengthens or shortens with a temperature change.Heat energy & specific heatHeat needed to change the temperature of a mass of material.Snell's law of refractionAngle of refraction as light passes between two media.Thin lens equationImage distance and magnification for a lens of known focal length.Doppler effect (sound)Observed frequency of a sound source moving relative to a listener.Sound intensity level (decibels)Decibel level of a sound from its intensity, referenced to the hearing threshold.Escape velocityMinimum speed to escape a body’s gravity from a given distance, ignoring drag.Circular orbital velocitySpeed and period needed to hold a circular orbit around a mass.Kepler's third lawOrbital period of a body from its orbit size and the mass it orbits.Buoyancy (Archimedes’ principle)Upward force on an object from the fluid it displaces, and whether it floats.Terminal velocityMaximum falling speed once drag balances gravity.Angular momentum (point mass)Rotational momentum of a point mass moving on a circular path.Resistor Colour Code CalculatorDecodes the coloured bands on a resistor into its resistance value and tolerance, for 4-band or 5-band resistors.Wire Size (AWG) CalculatorRecommends a copper wire gauge from current, cable run length and an acceptable voltage drop.DiopterOptical power in diopters from focal length, or focal length from a diopter value.Free Fall CalculatorFall time, distance and impact speed for an object dropped from rest, from any one of the three.Shear StressAverage and maximum shear stress in a material from a force acting parallel to a cross-section.Kinematic Viscosity of AirDynamic and kinematic viscosity of air at a given temperature and pressure.Parallel ResistorTotal resistance of up to four resistors wired in parallel, from the reciprocal-sum formula.ElongationHow much a bar or rod stretches under an axial load, from force, length and area.Friction Loss (pipe)Head loss and pressure loss from friction as water flows through a pipe.Enthalpy of ReactionEnthalpy change of a reaction from the total enthalpy of its products and reactants.y+ (Y-Plus) wall distanceDimensionless wall distance for CFD mesh sizing, and the cell height needed for a target y+.Average velocity (out and back)Average velocity versus average speed for a there-and-back journey, from two legs of distance and speed.Earth Curvature CalculatorHow much the Earth's surface drops (curves away) over a chosen horizontal distance.Engine DisplacementTotal swept volume of an engine from bore, stroke and cylinder count, in cc, litres and cubic inches.Semitone frequency shiftFrequency after shifting a note up or down by any number of semitones.Bernoulli's equationPressure at one point in a steady, frictionless flow from conditions at another point.Reynolds numberRatio of inertial to viscous forces in a flow, and whether it is laminar or turbulent.Coulomb's lawElectrostatic force between two point charges.Electric field of a point chargeField strength and potential at a distance from a single point charge.Magnetic field of a straight wireField strength at a distance from a long straight wire, from Ampère's law.Newton's law of universal gravitationGravitational force and potential energy between two masses.Time dilationHow much slower a clock moving at speed v runs, compared to a stationary observer.Length contractionHow much shorter a fast-moving object appears along its direction of motion.Mass-energy equivalenceEnergy contained in a rest mass, from Einstein’s E = mc².Mass-spring oscillator periodPeriod, frequency and peak speed of a mass bouncing on an ideal spring.Moment of inertia of standard shapesRotational inertia of common rigid shapes, and the resulting rotational kinetic energy.RLC circuit resonant frequencyResonant frequency, Q factor and bandwidth of a series RLC circuit.Photon energyEnergy of a single photon from its wavelength or frequency.De Broglie wavelengthWavelength associated with the momentum of any moving particle.Relativistic kinetic energyKinetic energy of an object moving fast enough that Newtonian mechanics breaks down.Wien's displacement lawPeak emission wavelength of a blackbody at a given temperature.Stefan-Boltzmann lawTotal power radiated by a hot surface, from its temperature and emissivity.Mach numberSpeed of an object relative to the local speed of sound in air.Shear Strain CalculatorShear strain from a lateral displacement and original length, or from the angle of deformation.Drag Coefficient CalculatorSolves for the drag coefficient (Cd) from a measured drag force, speed, fluid density and reference area.Telescope Field of ViewTrue field of view seen through a telescope and eyepiece combination, from focal lengths and the eyepiece apparent field of view.Quarter Mile CalculatorEstimated elapsed time and trap speed over a quarter mile from a vehicle’s weight and power, using a standard drag-racing approximation.Capacitive ReactanceCapacitive reactance of a capacitor at a chosen AC frequency, the opposition a capacitor presents to alternating current.Darcy Friction Factor CalculatorDarcy friction factor for pipe flow, from pipe roughness, diameter and Reynolds number.Wh (Watt-Hours) CalculatorEnergy used in watt-hours and kilowatt-hours from power draw and running time.Wire Gauge (AWG) CalculatorConverts an American Wire Gauge size to conductor diameter and cross-sectional area.Pitch Diameter CalculatorPitch diameter of a gear from its tooth count and diametral pitch or module.Von Mises Stress CalculatorEquivalent (von Mises) stress for a 2D plane-stress state, used to predict yielding under combined loading.Newton's Law of Cooling CalculatorTemperature of an object at a given time as it cools or warms towards its surroundings.Back Vertex DistanceHow a lens power changes when the distance between the lens and the eye changes.Angular FrequencyConverts between ordinary frequency, period and angular frequency (radians per second).Voltage Drop Calculator (mm2)Voltage drop along a cable run from its cross-sectional area, length, current and conductor material.Bore and Stroke CalculatorSolves for bore or stroke from a target engine displacement, using the reverse of the displacement formula.Hydraulic Radius CalculatorHydraulic radius of a rectangular, trapezoidal or circular channel from its cross-section and flow depth.Impedance CalculatorCombined AC impedance of a resistor with a capacitor or inductor, from Z = √(R² + X²).Sun Angle CalculatorSun elevation angle above the horizon from latitude, date and local solar time.Change in VelocityDelta-v from an initial and final speed, or from acceleration and time, with direction shown.Gay-Lussac's Law CalculatorPressure or temperature of a fixed gas volume after a change, using Gay-Lussac's Law.Lift Coefficient CalculatorSolves for the lift coefficient (Cl) from a measured lift force, air density, speed and wing area, or the reverse.Resultant Force CalculatorCombines two forces given as magnitude and angle into a single resultant force, with its magnitude and direction.Impact Force CalculatorAverage impact force from mass, speed and stopping distance, using the work-energy theorem.Wing Loading CalculatorWing loading of an aircraft or model, from total weight and wing area, in both metric and imperial units.Centre of Mass CalculatorBalance point of a system of point masses from their positions and masses.Thermal Conductivity CalculatorThermal conductivity of a material from heat transferred, thickness, area, temperature difference and time.Rotational Kinetic EnergyRotational kinetic energy of a spinning object from its moment of inertia and angular velocity.kW per TonneHVAC chiller efficiency: electrical power input divided by cooling capacity in tonnes of refrigeration.LMTD CalculatorLog mean temperature difference for a heat exchanger from the temperature differences at each end.Absolute Humidity CalculatorMass of water vapour per cubic metre of air, from temperature and relative humidity.LPH CalculatorFlow rate in litres per hour, minute and second, from a volume transferred and the time it took.Dipole Antenna LengthTotal length and leg length of a half-wave dipole antenna, from the operating frequency.Shear Force CalculatorMaximum shear force for a simply supported beam under a single central point load or a uniformly distributed load.Electric Motor Torque CalculatorTorque delivered by a motor from its power rating and shaft speed in RPM.dBm to Watt CalculatorConverts RF power between dBm, milliwatts and watts, and back again.Pressure Unit ConverterConverts pressure or stress between pascals, kilopascals, megapascals, bar, atmospheres, PSI and more.Relative Humidity CalculatorRelative humidity from dry-bulb air temperature and dew point, using the Magnus approximation.Wavenumber to Wavelength CalculatorConverts between wavenumber and wavelength using the spectroscopic convention (wavenumber = 1/wavelength).Heat Capacity CalculatorHeat energy to change the temperature of any mass, from a chosen or custom specific heat capacity.Simple harmonic motionPosition, velocity and energy of a mass-spring oscillator at a given moment.Beat frequencyHow fast two close sound frequencies pulse in and out of phase.AC power & power factorReal, reactive and apparent power in an AC circuit from RMS values and phase angle.Lensmaker's equationFocal length of a lens from its surface curvatures, thickness and refractive index.Schwarzschild radiusEvent-horizon radius of a black hole of a given mass, from general relativity.Mean free path of a gasAverage distance a gas molecule travels between collisions with other molecules.Wheatstone bridgeUnknown resistance from three known resistors at the balance point.Electron drift velocityAverage speed of charge carriers moving through a current-carrying wire.Redshift & blueshiftDoppler shift of light and the recession or approach velocity it implies.Compton scatteringWavelength shift of a photon scattered off a free electron at a given angle.RMS speed of gas moleculesRoot-mean-square speed of molecules in an ideal gas from temperature and molar mass.Malus's lawLight intensity transmitted through a polarizer at an angle to the polarization axis.Aerodynamic drag forceDrag force on an object moving through a fluid, from its shape and speed.Lever & mechanical advantageEffort force needed to balance a load on a simple lever, from the arm lengths.Center of mass (two bodies)Balance point of two masses along a line, and its distance from each.Heisenberg uncertainty principleMinimum combined uncertainty in the position and momentum of a quantum particle.Capacitors in series & parallelCombined capacitance of up to four capacitors, wired in series or in parallel.Incline with frictionForces and acceleration of an object sliding down a ramp with friction.Dry Bulb TemperatureOrdinary air (dry-bulb) temperature worked back from a wet-bulb reading and relative humidity.RPM ConverterConverts rotational speed between RPM, hertz and radians per second.Pounds-Force to Newtons ConverterConverts pound-force to newtons and back, the standard unit conversion for force, not mass.Gravitational Potential EnergyGravitational potential energy of an object from its mass, height and local gravity.Acceleration Due to Gravity CalculatorSurface gravity of any body from its mass and radius, using Newton’s law of gravitation.Magnitude of Acceleration CalculatorResultant acceleration from separate x, y and z component accelerations.Elastic Modulus CalculatorYoung’s modulus of a material from applied force, cross-sectional area and the resulting stretch.SCFM Airflow CalculatorConverts actual airflow (ACFM) at your working temperature and pressure to standard airflow (SCFM), the industry comparison figure.Wind Load CalculatorEstimates wind force on a flat surface from wind speed, air density, drag coefficient and area.Pneumatic Cylinder Force CalculatorExtend and retract force of a pneumatic cylinder from bore diameter, supply pressure and optional rod diameter.Heat Index CalculatorThe "feels like" temperature from air temperature and relative humidity, using the NOAA formula.Pulley Speed CalculatorDriven pulley speed and belt speed from driver and driven pulley diameters and driver RPM.Critical Damping CalculatorCritical damping coefficient of a mass-spring-damper system from its mass and spring constant.Lightning to Thunder Distance CalculatorEstimated distance to a lightning strike from the seconds between the flash and the thunder.Duty Cycle CalculatorDuty cycle percentage of a repeating signal from its on-time and total period.Wire Resistance CalculatorResistance of a length of wire from its length, diameter and material resistivity.Hydraulic Conductivity CalculatorHydraulic conductivity K from Darcy's Law, using flow rate, flow path length, cross-sectional area and head difference.Power Physics CalculatorMechanical power from work done and time, or from force and velocity, using the standard power formula physics.Free Space Path Loss CalculatorSignal loss in decibels over a given distance and frequency in ideal, obstruction-free conditions.Slenderness Ratio CalculatorA column’s slenderness ratio from its effective length and radius of gyration, used to gauge buckling risk.Angular Speed CalculatorAngular speed in radians, degrees and RPM, from an angle turned over time, a linear speed and radius, or a rotational speed in RPM.Orifice Flow CalculatorFlow rate through a sharp-edged orifice from its diameter, discharge coefficient and head.Thermal Equilibrium CalculatorFinal common temperature reached when two substances at different temperatures exchange heat until equilibrium.Power DissipatedElectrical power dissipated as heat in a resistor, from any two of current, voltage and resistance.Ground Speed CalculatorGround speed from true airspeed and a wind component, using vector addition.Piston Speed CalculatorMean piston speed from stroke length and engine RPM, used to compare engine designs.Muzzle Energy CalculatorKinetic energy of a bullet or projectile at the muzzle, from its weight and muzzle velocity, in joules and foot-pounds.WBGT CalculatorOutdoor Wet Bulb Globe Temperature, the heat-stress index used in sport and workplace safety, from wet-bulb, globe and dry-bulb readings.Poiseuille's LawVolumetric flow rate of a viscous fluid through a cylindrical pipe under laminar flow.Brewster's AngleAngle of incidence where reflected light becomes fully polarized, from two refractive indices.Solenoid Magnetic FieldMagnetic field strength inside a long, tightly-wound solenoid carrying a steady current.Force Between Parallel WiresMagnetic force per unit length between two long, straight, parallel current-carrying wires.Radiation PressurePressure an electromagnetic wave, like sunlight, exerts on an absorbing or reflecting surface.Angular VelocityRotational speed from the angle turned over time, plus linear speed at a given radius.RMS Voltage & CurrentRMS, average and peak-to-peak values of a sinusoidal AC voltage or current from its peak value.Recoil CalculatorEstimated recoil velocity and recoil energy of a firearm from bullet weight, bullet velocity and firearm weight.Pixel Density CalculatorScreen pixel density (PPI) from horizontal and vertical resolution and diagonal screen size.RAM latency (CAS latency to nanoseconds)Converts a CAS Latency (CL) spec into a real first-word access time in nanoseconds.Bolt torque to clamping forceTightening torque needed for a target bolt clamp load, using the standard T = K·D·F formula.Stellar Luminosity CalculatorA star's total power output from its radius and surface temperature, using the Stefan-Boltzmann law.Spring Constant CalculatorSolves Hooke's Law for the spring constant k, given a measured force and displacement.Kpag to Kpa (Gauge to Absolute Pressure)Converts a gauge pressure reading in kPa to absolute pressure by adding atmospheric pressure.Open Channel Flow CalculatorFlow rate through an open channel from cross-sectional area, hydraulic radius, slope and Manning's roughness coefficient.Drone Flight Time CalculatorEstimated flight time for a drone from battery capacity, average current draw and a reserve margin.Principal Stress CalculatorMaximum and minimum principal stresses and maximum shear stress for a 2D stress state, using Mohr’s circle.Effective Nuclear Charge CalculatorEffective nuclear charge (Zeff) felt by an electron, using Slater's Rules from the atomic number and subshell.Torsional Stiffness CalculatorTorsional stiffness of a solid circular shaft from shear modulus, diameter and length.Lumens to Candela CalculatorConverts light output in lumens to luminous intensity in candela, or back, over a chosen beam angle.Camera Field of View CalculatorHorizontal and vertical field of view in degrees, from sensor dimensions and lens focal length.Thermal Resistance CalculatorFinds the thermal resistance (R-value) of a material layer from its thickness, area and thermal conductivity.Hazen-Williams pipe head lossFriction head loss along a pipe using the Hazen-Williams empirical formula for water.J-pole antenna dimensionsRadiator, stub and feedpoint dimensions for a J-pole antenna at a given frequency.Signal propagation delayTime a signal takes to travel a distance through cable, fibre or free space.Transmission (serialisation) delayTime to clock a packet onto a link at a given bandwidth, and the total with propagation.Ideal Rocket EquationVelocity change a rocket can achieve from its exhaust velocity and the propellant mass burned.Bragg's LawDiffraction angle for X-rays reflecting off crystal lattice planes at a given spacing.Rydberg EquationWavelength of light from an electron jumping between energy levels in a hydrogen-like atom.Stokes' Law Terminal VelocityFalling speed of a small sphere through a viscous fluid once drag balances its weight.Cyclotron FrequencyOrbital frequency of a charged particle circling in a uniform magnetic field.Distance to the HorizonGeometric sight distance to the horizon from an observer height above a sphere.Angular AccelerationRate of change of angular velocity over a time interval, from spin-up or spin-down.G-Force from AccelerationHow many g's a change in velocity over time represents, relative to standard gravity.Magnetic Dipole MomentStrength of the magnetic moment produced by a current flowing around a coil loop.Thermal DiffusivityHow quickly a material equalises temperature, from conductivity, density and specific heat.Poisson's RatioHow much a material bulges sideways when stretched or squeezed lengthways.Shear ModulusStiffness of a material against sideways (shear) deformation from an applied force.Specific ImpulseHow efficiently a rocket or jet engine converts propellant into thrust.Froude NumberRatio of flow inertia to gravity in open-channel or ship-hull flow.Hall CoefficientCharge-carrier density and sign in a conductor from a measured Hall voltage.Hoop StressCircumferential and longitudinal stress in a thin-walled pressure vessel.Synodic PeriodTime between successive alignments of a body with Earth, or another chosen reference body.Skin DepthDepth below a conductor surface where AC current density falls to 1/e of its surface value.Boyle's LawPressure or volume of a fixed gas amount after an isothermal change, from the other values.Photoelectric EffectKinetic energy and stopping voltage of electrons ejected from a metal by light.Blackbody RadiationSpectral radiance a hot object emits at one wavelength, from Planck's law.Hubble's LawRecession speed of a distant galaxy from its distance and the Hubble constant.Black Hole TemperatureHawking temperature and evaporation timescale of a black hole from its mass.Drake EquationOrder-of-magnitude estimate of communicating civilisations in the galaxy from seven factors.Hydrogen-Like AtomElectron energy level and orbital radius in a one-electron atom or ion, from the Bohr model.Diffraction GratingAngle at which a given order of light diffracts off a grating of known line spacing.Friction ForceFriction force resisting motion on a flat or inclined surface, from mass and coefficient.Angle Of ReposeSteepest stable slope angle for a granular pile from its static friction coefficient.Coriolis EffectCoriolis acceleration and force on a moving mass from its speed and latitude on Earth.Gear RatioOutput speed and torque of a gear pair from the tooth counts and the input speed.Latent HeatHeat energy absorbed or released during a phase change from mass and the specific latent heat.Weight On Other PlanetsHow much a mass would weigh on the Moon or another planet, from each body’s surface gravity.Speed of light travel timeHow long light takes to cross a distance, or how far it travels in a given time.Speed of sound in airSpeed of sound in air from temperature, plus how far it travels in a given time.Acceleration from initial and final speedUniform acceleration from a starting speed, an ending speed and the time taken.

Home & build

Quantities and sizing for renovation, landscaping and trade work: paint, tiles, concrete, timber and roofing, with the waste allowance on each.

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Paint requiredLitres of paint for walls, allowing for doors and windows.Flooring & tilesBoxes of tiles or boards needed, including wastage.Concrete volumeCubic metres for a slab, footing or set of posts.Mulch, soil & gravelBulk material for a garden bed at a given depth.Roof pitch & rafter lengthAngle, slope factor and true roof area.Fencing & decking materialsPosts, rails and boards for a run of fence or deck.Air conditioner sizingCooling capacity for a room, adjusted for sun and occupancy.Tank & pool volumeCapacity of a rectangular or round tank in litres.Soil CalculatorHow much soil or potting mix is needed to fill a garden bed, raised bed or pot, in volume and bags.Decking CalculatorDeck area, boards needed, screws and an estimated material cost from your deck dimensions.Steel Plate Weight CalculatorWeight of a steel plate from its length, width and thickness, with an editable density.Drywall sheets neededPlasterboard sheets for a room, allowing for openings and waste.Bricks or blocks neededMasonry units for a wall, from unit size and mortar joint thickness.Stair rise & runStep count, riser height and comfort check for a straight staircase.Pavers & bedding sandNumber of pavers and bedding sand volume for a patio or path.Roof shingle bundlesBundles of shingles needed, accounting for slope and waste.Board feet of lumberBoard feet and cost for a batch of dimensional lumber.Baluster / spindle spacingEven spindle count and gap for a stair or deck railing.Wallpaper rolls neededRolls required for a room, accounting for pattern repeat.Wall stud countStuds needed for a wall on a chosen centre spacing, plus openings.Ladder angle & base distanceSafe base distance and length for a leaning ladder, using the 4-to-1 rule.Insulation thickness & coverageThickness needed to hit a target R-value, and rolls required for an area.Beam DeflectionMaximum deflection of a cantilever or simply-supported beam under a point load, from its length, load and stiffness.Bending StressMaximum bending stress in a beam from the applied bending moment, distance to the extreme fibre and second moment of area.Pipe Volume CalculatorInternal volume a pipe can hold in litres and cubic metres, from outer diameter, wall thickness and length.Gravel CalculatorVolume and weight of gravel needed for an area and depth, with an editable density and bag size.Glass Weight CalculatorWeight of a flat glass pane from its length, width and thickness, with an editable density for different glass types.Concrete Weight CalculatorWeight of a concrete slab, footing or block from its dimensions, with an editable density.Pitch CalculatorRoof pitch as a rise:run ratio, angle in degrees and slope percentage, from rise and run measurements.Sand CalculatorVolume and weight of sand needed for an area and depth, with an editable density and bag size.Pipe Fall CalculatorDrainage or pipe fall in mm of drop per metre of run, for a given slope angle in degrees.Aluminium Sheet Weight CalculatorWeight of an aluminium sheet or plate from its length, width and thickness, with an editable density.Tonnage CalculatorEstimated air conditioning tonnage needed for a room or building, from its floor area and a climate guideline.Mitre Cut CalculatorMitre saw angle needed on each piece to join two pieces of trim or framing at a given corner angle.Fence Picket SpacingHow many pickets fit a fence run at a chosen width and gap, adjusted to fit evenly.Lawn Mowing Cost CalculatorEstimated cost per mow and per year for a lawn, from your own area and price inputs.Road Base CalculatorVolume and weight of road base needed for a driveway or path, with an editable density and bag size.Brick Course Height CalculatorHeight of one brick course, and how many courses reach a target wall height.CFM Airflow CalculatorAirflow in cubic feet per minute, from duct area and air velocity, or from room volume and air changes per hour.Balustrade Spacing CalculatorHow many balusters fit a railing run within a maximum allowable gap, adjusted to fit evenly.GPM to LPM CalculatorConverts flow rate between gallons per minute and litres per minute, US or imperial gallon, either direction.Carpet quoteTotal carpet cost for a room from area, carpet price per m², underlay and installation.Belt Length CalculatorLength of a flat or V-belt wrapped around two pulleys, from their diameters and centre distance.Door / window header sizeMinimum header depth for a rough opening, using the standard light-framing rule of thumb.Fence post hole depthHow deep to set a fence or deck post below grade, and the total post length to buy.Post hole concreteConcrete needed to set posts in round holes, allowing for the post itself.Board and batten sidingBattens needed to cover a wall at a chosen spacing, plus base board coverage.French drain materialsGravel and pipe needed for a French drain trench.Rebar for a concrete slabBar count and total length for a two-way rebar grid in a slab or footing.Tile grout neededWeight of grout for a tiled area, from tile size and joint dimensions.Ramp slope & lengthSlope ratio, angle and ramp length for a given rise, checked against the ADA maximum.Bending MomentMaximum bending moment in a simply-supported or cantilever beam, from its load and span.Wall Stud Spacing CalculatorNumber of wall studs needed for a wall length at a chosen on-centre spacing.Concrete Cylinder StrengthCompressive strength of a standard concrete test cylinder from its failure load.Moisture Content CalculatorMoisture content of a material from wet and dry weight, on either a wet basis or a dry basis.Pavers Need CalculatorNumber of individual pavers needed to cover an area, from paver size and a waste allowance.Shed Cost EstimatorRough materials cost for a shed from floor area, a materials price per m², and optional slab, roofing and extra costs.Mortar CalculatorMortar volume and bags needed for a brick or block wall, from wall size and joint thickness.Cubic Volume CalculatorVolume of a rectangular box from length, width and height, in cubic metres, cubic feet and litres.Concrete Mix Ratio CalculatorCement, sand and aggregate quantities for a target volume, from any editable mix ratio.Steel Bar Weight CalculatorWeight of a round steel bar or rod from its diameter, length and density.1 in X Fall Ratio CalculatorConverts a drainage or slope ratio written as "1 in X" into an actual fall in mm over a given run length.Battery Amp Hour CalculatorAmp-hour capacity needed to run a known current draw for a set number of hours.Miter Cut Angles CalculatorThe miter angle to cut on each piece of a regular multi-sided frame, from the number of equal sides.Ha per Hour CalculatorWork rate in hectares per hour from an area covered and the time taken, or the time needed to cover a target area at that rate.GPM CalculatorWorks out flow rate in gallons per minute from a volume of liquid and the time it took to move.Retaining wall blocksNumber of retaining wall blocks for a wall from its length, height and block size.Deck footing countNumber of footings for a deck frame at a chosen maximum footing spacing.Well water volumeWater volume held in a well casing from its diameter and the water column depth.Roof truss countNumber of roof trusses for a building length at a chosen on-centre spacing.Board-on-board fenceBoards, posts and rails for a board-on-board fence, from the board overlap.Taper CalculatorTaper ratio and included angle of a shaft or workpiece from its large diameter, small diameter and length.Fabric CalculatorLength of fabric needed for a rectangular project, from its dimensions, fabric width and a wastage allowance.Thread Pitch CalculatorConvert between metric thread pitch and threads per inch (TPI) for screws, bolts and taps.Battery Charging Time CalculatorHours to charge a battery from its amp-hour capacity, current charge state and charging current.Sandstone Block Weight CalculatorWeight of a rectangular sandstone block from its length, width, height and density.Metric Thread CalculatorMajor, pitch and minor diameter, and tap drill size, for a standard ISO metric thread designation.Slope Percentage CalculatorConverts a rise and run into a percentage grade and an angle in degrees, for ramps, driveways or any general slope.Silicone Sealant CalculatorCartridges of silicone sealant or caulk needed for a run of joints, from bead size and cartridge volume.Roof Truss Cost Australia CalculatorTotal roof truss cost from the truss count needed for a building length and a free price per truss.Picket Spacing CalculatorHow many pickets fit a fence run and the actual evenly-distributed gap between them.Timber Beam Span CalculatorSimplified deflection check for a simply-supported timber beam under a uniform load, as a rough guide only.Vinyl Flooring Cost CalculatorTotal cost of vinyl flooring from area, price per square metre and wastage.Timber Weight Australia CalculatorWeight of a length of timber from its dimensions and species density, with common Australian species as presets.Stair Angle CalculatorStair pitch angle from total rise and run, with per-step rise and going and a code-comfort check.Occupancy Load CalculatorMaximum occupancy for a floor area, from a chosen occupant load factor per square metre.Square Footage CalculatorWork out the area of a room or space in square feet from its length and width.Wall Framing Stud CalculatorHow many studs a wall needs at a chosen spacing, plus the plate timber, allowing for openings and corners.Pipe Grade and Fall CalculatorConverts a drainage pipe grade into the fall over a run, in either direction, as a ratio, percentage and angle.Speaker Box Internal Volume CalculatorInternal volume of a rectangular speaker enclosure from its external dimensions and panel thickness.Rainwater harvesting yieldWater a roof collects from a given rainfall, and how long a tank takes to fill.Pipe weightWeight of a length of hollow pipe from its diameter, wall thickness and material.Rolling offset (pipefitting)True offset, travel and run for a pipe that must dodge an obstacle both sideways and up.Concrete block core fillGrout volume to fill the hollow cores of concrete masonry blocks.Insulation upgrade paybackYearly energy saved by raising the R-value of one building element, and how long the upgrade takes to pay for itself.Septic tank sizingWorking volume and sludge allowance for a septic tank from occupancy, daily flow and retention time, with the desludging interval it implies.Floor area ratio (FAR)Ratio of building floor area to lot size, and the max floor area a zoning FAR limit allows.Paver sand neededVolume and weight of bedding or joint sand needed to cover a paver area at a given depth.Arch radius from rise and spanRadius of the circular arc that gives a doorway or window arch its rise and span.Sheet metal bend allowanceFlat pattern length added by a bend, from thickness, radius, angle and the K-factor.Sheet metal punch forceForce needed to punch a hole through sheet metal, from the hole perimeter and material.Bolt circle spacingStraight-line spacing between adjacent bolt holes evenly spaced on a bolt circle.Air changes per hourHow many times an hour a ventilation system replaces a room's air.Bathroom mirror sizeRecommended mirror width and height from your vanity and ceiling.Furnace size (BTU)Heating capacity needed for a home, from floor area, climate band and insulation.Metal bar & sheet weightWeight of a metal plate, bar or round rod from its dimensions and material density.Lumber weightWeight of dimensional lumber or a stack of boards, from species density and count.

Everyday

Practical comparisons for shopping, travel, cooking and time: the small calculations that add up, from unit pricing to fuel costs and tipping.

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Trip fuel costFuel and time for a journey, split between passengers.Unit price comparisonWhich pack is actually cheaper per unit.Recipe scalerRescales quantities and adjusts baking time.Aspect ratio & screen sizeResize while keeping proportions, or find screen dimensions.Pizza & round-item valueArea per dollar: the honest way to compare sizes.Reading & speaking timeHow long a word count takes to read aloud or silently.Password strengthEntropy in bits and how long a brute force would take.Coffee brew ratioGrounds and water for a chosen strength.Hours of work to buy somethingPrices a purchase in hours of your life.Words per minuteReading speed in words per minute, from a word count and the time it took to read.Weekly work hoursAdds up hours worked across a week from a daily figure, with an overtime threshold.Minutes in a dayHow many minutes are in a day, or in any number of days, hours or weeks.SubnetNetwork address, broadcast address and usable host range for an IPv4 address and CIDR prefix.Working days left in the yearWeekdays remaining from any date to 31 December that year, and the year's full working-day total.Day counterA running day count from a start date to today or any other date, framed as "Day N".Hours in a yearHow many hours are in a year, for a common, leap or average calendar year, or a number of years.Week Number CalculatorISO week number for any date, or the date range covered by a given week and year.Bold Text Generator (Unicode)Turns typed text into Unicode bold, italic or bold-italic characters that paste as real formatting anywhere.Fuel Consumption CalculatorWorks out your actual fuel consumption rate from a distance travelled and the fuel used, in L/100km, km/L and mpg.Date and time calculatorAdds or subtracts days, hours and minutes together from a single starting date and time.Date duration calculatorThe gap between two dates expressed as a single total in years, months, weeks and days at once.Day of the year calculatorWhich numbered day of the year, from 1 to 365 or 366, any date falls on.Superscript GeneratorTurns typed text into Unicode superscript characters, for exponents, footnotes and ordinal-style text.What Year Will It Be CalculatorThe calendar year a chosen number of years and months from any starting date.Nether Portal CalculatorOverworld to Nether coordinates and back, using the fixed 8:1 ratio.Aspect Ratio (16:9 & more)Matching width or height for a target ratio like 16:9, or the simplified ratio of two sizes.Business Days in a MonthCounts the weekdays in any calendar month, minus any public holidays that fall on one.Pig Latin TranslatorTranslates English text into Pig Latin, moving each word's leading consonants to the end and adding "ay".Wedding Anniversary CalculatorYears married, the traditional gift for that anniversary year, and days until the next one, from a wedding date.Shoe Size ConverterConverts a shoe size between US, UK and EU sizing for men's or women's shoes.Upside-Down Text GeneratorFlips typed text into upside-down Unicode characters, reversed to read correctly when inverted.Small Text GeneratorTurns typed text into small Unicode capital letters that paste as smaller-looking text anywhere.Title Case ConverterCapitalises a piece of text into title case, following the AP style rule of lower-casing minor words except at the start or end.Electricity Bill CalculatorEstimates a power bill from usage in kWh, your rate per kWh, and any fixed daily supply charge.Months Between Two DatesWhole months and remaining days between two dates, plus the total as a decimal.Circle Skirt CalculatorFabric radius needed for a full, half or other fraction circle skirt from waist and skirt length.RAID CalculatorUsable storage capacity and fault tolerance for RAID 0, 1, 5, 6 and 10 arrays.Travelling Time by CarDriving time from distance and average speed, plus an allowance for traffic and stops.D&D 5e Point Buy CalculatorSpends a 27-point budget on the six D&D 5e ability scores, using the official fixed cost table.Jeans Size CalculatorConverts a US jeans size to UK, EU and waist measurement, for men's or women's cuts.Birth Year CalculatorWorks out the possible birth year for someone at a given current age, as a range of two years.Subscript GeneratorTurns typed text into Unicode subscript characters, for chemical formulas and footnote indices.Check Expiry Date CalculatorWorks out the expiry date from a purchase date and shelf life, and how many days remain.Hair Grow in Month CalculatorTotal hair growth over a number of months at a chosen, editable monthly growth rate.Vocal Range CalculatorClassifies a voice type, bass to soprano, from a lowest and highest comfortable note.eDPI (Effective DPI)Mouse DPI multiplied by in-game sensitivity, the number used to compare sensitivity across games and mice.Calendar CalculatorDay of the week, ISO week number, quarter and day of year for any date.Age Difference CalculatorYears, months and days between two people's dates of birth, and who is older.Elapsed Time CalculatorElapsed time between a start date and time and an end date and time, in days, hours, minutes and seconds.Hair Length Chart CalculatorMatches a hair length in inches or cm to the closest category on a standard hair-length chart.Mayan Calendar ConverterConverts a Gregorian date to the Mayan Long Count, Tzolkin and Haab calendar dates, using the standard GMT correlation.Cursive Writing GeneratorTurns typed text into Unicode cursive-style mathematical script characters that paste as styled text anywhere.Hours in a Week CalculatorHow many hours are in a week, or any chosen number of weeks, from the fixed 168-hour week.US Coin Value CalculatorTotal dollar value from a count of US pennies, nickels, dimes, quarters, half-dollars and dollar coins.Caesar Cipher CalculatorEncodes or decodes text with a Caesar shift cipher, or tries all 25 shifts when the shift is unknown.Case Sensitive Text ComparisonCompares two pieces of text and shows whether they match case-sensitively and case-insensitively.Add Time CalculatorAdds two or more time durations together (hours, minutes and seconds) to get a combined total duration.Watts to Watt Hours CalculatorConverts power in watts and a running time into energy used in watt-hours and kilowatt-hours, with an optional cost estimate.Baby Age CalculatorA baby or infant’s current age in weeks and months from their date of birth, not just years.Ring Size ConverterConverts between US/Canada ring sizes, UK/Australian letter sizes, EU sizes and finger circumference or diameter.Korean ageTraditional Korean age from a birth year, and the difference from international age.Fish Tank Gallons to LitresConverts a fish tank size between US gallons and litres, either direction, using the exact 3.78541 L per US gallon factor.TV Mounting HeightThe recommended height for the centre of a TV screen above the floor, based on seated eye level.Poker Hand StrengthRanks a 5-card poker hand into its standard category, from high card up to a royal flush.Years Between Two DatesThe span between two dates expressed as decimal years, plus the whole-years-and-days breakdown.Battery charge timeHow long a device takes to charge from its current level to a target level.Typing speed (WPM)Gross and net words per minute, and accuracy, from a timed typing sample.Luggage linear inchesChecks a bag against an airline’s combined length + width + height limit.Cost of a meetingWhat a meeting actually costs in attendee salary time.True cost per mile to driveAll-in running cost of a vehicle, spread across the miles driven.Weight of a pile of cashHow much a dollar amount weighs in bills or coins.2-stroke fuel mix ratioOil to add to a volume of petrol for a chosen mix ratio.Generator sizingGenerator capacity needed to cover a set of appliances, including starting surge.LED bulb savingsElectricity and replacement-bulb savings from switching to LED lighting.Event tables & seatingTables needed for a guest count, for round or rectangular tables.Pomodoro session plannerHow many focused work intervals a task will take, breaks included.Money saved by quitting smokingWhat not buying cigarettes adds up to over time.Roll length remainingHow much material is left on a roll, from its diameter and material thickness.Cost of a showerWater and water-heating energy cost for one shower.EV home charging cost & timeCost and time to charge an electric vehicle from one charge level to another.Binge-watch time plannerTotal time to finish a TV series, and how many days that takes.Moon phase finderThe approximate Moon phase on any date, from the lunar synodic cycle.Weighted blanket sizeRecommended blanket weight from body weight, using the common 10% rule.Mobile data usageDaily and monthly data use from your everyday activities, and how long a data cap will last.Gold Weight CalculatorWeight of a gold item from its volume and karat purity, with density editable for custom alloys.Morse Code TranslatorConverts text to Morse code or Morse code back to text, covering letters A-Z and digits 0-9.Half Birthday CalculatorThe date exactly six months after (or before) a birth date, and how many days until it next falls.TV Size CalculatorRecommended TV screen size from viewing distance, or recommended viewing distance from screen size.Tie Length CalculatorRecommended necktie length for a given height, using standard, short and long/XL sizing bands.Dilution Ratio CalculatorConcentrate and water needed for a mixing ratio such as 1:10, from the total volume you need to make up.Paving cost estimateEstimated material and labour cost to pave an area, from your own price and waste inputs.Playback SpeedNew watch time and time saved when a video or audio track is played faster or slower.Weeks Left in the Australian Financial YearWeeks and days remaining until 30 June, the end of the Australian financial year.KD (Kill/Death) Ratio CalculatorKill/death ratio from a kill count and a death count, the core gaming performance stat.Age From Birth Year CalculatorCurrent age from a birth year alone, as a range of two possible ages.Steps to weight lossEstimated calories burned from a daily step count, and the resulting weight change over a chosen period.D&D 5e Hit Points CalculatorCharacter hit points at any level, using the 5th-edition SRD hit die and Constitution rules.Microwave Wattage ConverterAdjusts a recipe cooking time from one microwave wattage to another.Dress Size CalculatorConverts a US womens dress size to the equivalent UK, EU and Australian size numbers.Paper Thickness CalculatorWorks out the thickness of a single sheet from a measured stack, or the height of a stack from a known sheet thickness.Minecraft Stack CalculatorConverts a Minecraft item count to stacks and leftover items, or stacks back to a total, with an editable stack size.Days in a Month CalculatorHow many days a given month has, including whether a February falls in a leap year.Leetspeak (1337) ConverterConvert plain text to leetspeak, or decode common leetspeak back to letters.ASCII ConverterConverts text to its ASCII decimal and hex codes, or decodes a list of ASCII codes back to text.Acre SizeHow big an acre actually is, in square feet, square metres, square yards and hectares.Music Note DurationHow long a musical note lasts in seconds and milliseconds, at a given tempo.Carpool cost sharingSplits a shared commute's fuel cost fairly among riders.Commute cost & time comparisonCompares driving to public transit for a regular commute, in cost and time.Toilet paper: how long a pack lastsHow many days a pack of toilet roll lasts a household, from usage per person.Firewood needed for the seasonHow many cords of firewood a heating season needs, from stove burn rate and heating days.Tire size & speedometer differenceOverall diameter, circumference and speedometer error between two tire sizes.Crosswind & headwind componentSplits a wind reading into the part blowing across your path and the part blowing along it.Packing boxes estimateHow many moving boxes a household will need, from room count plus kitchen and fragile items.Cost Per Unit CalculatorCost per single unit from a total cost and the number of units, for production, buying in bulk or pricing.Reading Time by Page Count CalculatorHow long it takes to read a given number of pages, from an editable words-per-page figure and reading speed.Fuel Range CalculatorEstimated distance a vehicle can travel on its remaining fuel, from tank amount and consumption rate.Minutes Between Two Times CalculatorMinutes, and hours and minutes, elapsed between two clock times on the same or the next day.Curtain SizeCurtain width and drop from your window or rod size, a fullness ratio and where the hem should sit.Underline Text GeneratorTurns typed text into underlined-looking Unicode text by inserting a combining low line after every character.Future Age CalculatorWorks out how old you will be in a chosen future year, from your current age and the current year.Beats Per Minute (BPM) CalculatorTurns a beat count over a timed interval into a rate per minute, for a pulse or a musical tempo.Song Length CalculatorEstimates a song’s length from its tempo, beats per bar and number of bars.Harry Potter Currency ConverterConverts Galleons, Sickles and Knuts using the fixed wizarding exchange rates, both ways.Belt sizeBelt size to buy from a waist measurement, using the standard buckle allowance.Standing desk heightStanding desk surface height from your height, using the elbow-height ergonomic ratio.Screen viewing distanceRecommended seating distance from a screen size and target field of view.Sunscreen amountSunscreen to apply per full-body application, from the dermatology 2 mg/cm² rule.Hammock hang angleRidgeline length and hang-point drop for a comfortable hammock sag between two anchors.Time Percentage CalculatorWhat percentage of a day or any other period a given duration represents, and the reverse.Uptime CalculatorConverts an uptime percentage such as 99.9% into the equivalent allowed downtime per year, month, week and day.Day Number to Date CalculatorTurns a day-of-year number (1-366) into the actual calendar date for a chosen year.Paper Quantity ConverterConverts between individual sheets, quires and reams of paper using standard paper-trade quantities.Text Case ConverterConverts a block of text to lower case, UPPER CASE or Title Case.Plant Spacing CalculatorHow many plants fit a garden bed at a chosen spacing, in a grid pattern.Chinese Age CalculatorTraditional Chinese (East Asian) age, counted as 1 at birth and rising by one at each Lunar New Year.File Transfer Speed CalculatorThe effective transfer speed of a completed file transfer, worked backwards from file size and the time it actually took.Dimensional (Volumetric) Weight CalculatorWorks out a parcel’s dimensional weight from its dimensions, and compares it against the actual weight to find the chargeable weight couriers use.Forced induction boost & pressure ratioPressure ratio, density gain and effective displacement from a boost pressure.Engine compression ratioStatic compression ratio for an engine cylinder from bore, stroke and clearance volume.Cross-stitch fabric sizeFabric size to buy for a cross-stitch pattern, from stitch count, fabric count and margin.Bean bag fillingFiller needed for a bean bag chair from its filled dimensions, using the standard bead density.Clay shrinkageFired size of a clay piece after drying and firing shrinkage, from its wet (greenware) size.Sidereal timeLocal sidereal time for a date, UTC time and longitude, the star clock astronomers use.EV vs petrol running costCompares the energy cost of driving electric against petrol over a year, and finds the prices at which the two break even.Towing capacity and payloadChecks a loaded vehicle and trailer against its payload, gross vehicle mass, combination mass and towing limits, and finds which one binds first.Balloon arch balloon countBalloons needed for a single-row or garland balloon arch from its size and balloon diameter.Cost per minuteBreaks a total cost down to a rate per minute, for calls, rentals, or metered time.Tablecloth sizeTablecloth dimensions needed for a table, from its size and how far you want the drop.Curtain fabric neededFabric width and panel count for curtains, from window size and desired fullness.Pool salt neededHow much salt to add to a saltwater pool to reach a target concentration.Bath vs. shower water useCompares the water used filling a bath against taking a shower of a given length.Hat sizeHat size number from head circumference, plus the letter size.Glove sizeGlove size number and letter size from a hand circumference measurement.Paper sheet & ream weightWeight of a sheet or a stack of paper from its GSM and dimensions.Helium balloon liftHow many balloons of a given size are needed to lift a payload.Winch sizeRecommended winch pulling capacity from vehicle weight and a safety factor.Lumens to wattsPower draw needed for a target brightness, by bulb technology.Event tent sizeFloor area and footprint needed for a party or event tent, by seating style.Toothpaste tube lifeHow many days a toothpaste tube lasts a household, from tube size and brushing habits.Days until ChristmasA countdown to the next 25 December, worked out from any starting date.Days in a year or monthHow many days are in any year or month, with the leap year worked out for you.Anniversary calculatorYears, months and days since an anniversary date, and when the next one falls.Date calculatorAdd or subtract days, weeks, months or years from any date.Hours calculatorHours and minutes between two clock times, including overnight spans.Days calculatorHow many days between two dates, counted either way.Time between datesFull breakdown of years, months, weeks and days between two dates.Difference between two numbersAbsolute difference, percentage difference and percentage change between two numbers.Months calculatorWhole months and remaining days between two dates, or a set number of months between them.Weeks in a monthHow many calendar weeks a given month spans, based on its day count and starting weekday.Leap year checkerWhether any given year is a leap year, using the 4/100/400 rule, plus the nearest leap years either side.Days until a dateHow many days from today until any target date you enter, or how many days have passed if it is behind you.Weeks between two datesWhole weeks and remaining days between two dates, plus the total as a decimal.Days till Christmas in AustraliaA countdown to the next 25 December, with the Australian summer Christmas context.

Growth

Growth rates for revenue, users and any other metric that moves period to period: YoY, MoM, QoQ and beyond, each with its own dedicated page.

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Year-over-year (YoY) growthGrowth between this period and the same period a year ago.Month-over-month (MoM) growthGrowth between this month and last month, with the annualised equivalent.Quarter-over-quarter (QoQ) growthGrowth between this quarter and the previous quarter, with the annualised equivalent.Week-over-week (WoW) growthGrowth between this week and last week, with the annualised equivalent.Day-over-day (DoD) growthGrowth between today and yesterday, with the annualised equivalent.Period-over-period (PoP) growthGrowth between any two comparable periods you define, with a custom annualising cadence.Compound monthly growth rate (CMGR)The smooth monthly rate that links a start and end value over several months.Annualised run rateExtrapolates a single period of revenue to a full-year figure.Rule of 40Checks whether growth rate plus profit margin clears the 40% SaaS health benchmark.User & customer growth rateNet growth rate for a user base once new signups and churned users are both counted.Revenue growth & target plannerGrowth achieved between two periods, and the revenue needed next period to hit a target rate.

Food

Kitchen and brewing ratios: baker’s percentages, hydration, dilutions, yields and the maths behind a recipe that scales without going wrong.

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Grams in a Teaspoon of PowderWeight in grams of a teaspoon of a common powdered ingredient, such as flour, cocoa or baking soda.ABV CalculatorAlcohol by volume of a mixed drink blended from several components of different strengths.Grams to Teaspoons ConverterConverts between grams and teaspoons for common baking and cooking ingredients, in either direction.Food CalorieTotal calories in a meal from protein, carbohydrate and fat grams, using the 4/4/9 rule.Baker’s percentage & hydrationExpresses each dough ingredient as a percentage of the flour weight, as bakers do.Brine strengthSalt needed to make a brine of a given strength, by weight of the water.ABV from gravity readingsAlcohol by volume of a home-brewed beer or wine from hydrometer readings.Alcohol dilutionWater needed to cut a spirit down from one ABV to a weaker target ABV.Yeast type converterA quantity of yeast converted between active dry, instant and fresh (cake) forms.Self-rising flour from all-purposeBaking powder and salt to turn plain flour into self-rising flour.Rice to water ratioWater needed to cook a given amount of rice, and the approximate cooked yield, by rice type.Dry to cooked pasta weightHow much a portion of dry pasta weighs once boiled, given its typical expansion factor.Party drink plannerTotal drinks needed for a party, split across beer, wine and spirits.Cake servingsHow many servings a round or rectangular cake yields at a given slice size.Ice cream overrunHow much the volume of a churned ice cream mix has grown from the air whipped into it.Plain Flour to Self Raising Flour CalculatorHow much baking powder to add to plain flour to make self-raising flour, standard ratio.Catering Amount Per PersonHow much rice, popcorn kernels or pizza to buy for a group, using standard catering serving guidelines.Uncooked to Cooked Rice CalculatorConverts uncooked rice weight to cooked weight, or back, using a typical published cooking ratio by rice type.Steak Cooking TimePan-sear or grill time per side for a steak, by thickness and desired doneness.Cups to grams (ingredient weight)Converts a volume measure of a common ingredient to weight, using typical ingredient density.Turkey roasting & thawing plannerOven time and refrigerator/cold-water thawing time for a turkey, from its weight.Cake pan size converterRescales a recipe's batter amount when swapping to a different pan shape or size.BBQ / party food plannerProtein, sides and drinks to buy for a barbecue or party, per guest.Alcohol For PartyTotal drinks needed for a party, from guest count, event length and an editable drinks-per-hour rate.Pounds to Cups (Dry Ingredient)Converts pounds of a dry ingredient to cups using an editable weight-per-cup figure.Kilojoules from MacrosTotal kilojoules in a food or meal from its protein, fat and carbohydrate content.Ham per personHow much ham to buy for a group, by bone-in or boneless serving guidelines.Priming sugarSugar to add for bottle-carbonating a home-brewed beer to a target CO2 level.Cake pricingA sale price for a custom cake from ingredient cost, labour and a target profit margin.Meat per Person for a BBQTotal meat to buy for a barbecue from guest numbers and a chosen amount per person.Cake Tin Conversion CalculatorScales a recipe from one cake tin size to another using the ratio of their baking areas.Pizzas For A Group CalculatorNumber of pizzas to order for a group, from guest count, slices per person and slices per pizza.Fresh to dried herb conversionDried herb amount to substitute for a fresh herb quantity in a recipe, or the reverse.Garlic form converterEquivalent amount of minced, powdered or granulated garlic for a number of fresh cloves.Air fryer conversionConverts an oven recipe to an air fryer by dropping the temperature and shortening the time, with a first check well before the end.Turkey thawing timeTime needed to safely thaw a turkey in the refrigerator or in cold water, by weight.Bacon curing ratiosDry-cure salt, pink curing salt and (for wet brining) water for a pork belly, by weight.Molecular SO2 in wineThe antimicrobially active molecular SO2 fraction, from free SO2 and wine pH.Drink chilling timeTime for a drink to cool to a target temperature, using Newtons law of cooling.Ham cooking timeOven roasting time for a ham, from its weight and whether it is fully cooked or fresh.Mashed potatoes per personHow much mash to make and how many raw potatoes to buy for a group.BBQ grill sizeGrilling surface area needed for a cookout, and an equivalent round grill diameter.Egg boiling timeBoiling time for an egg by size and doneness, scaled from a large-egg baseline.Tea steeping guideRecommended water temperature and steep time by tea type, and leaves needed for a batch.Oil to butter converterConverts a recipe quantity between cooking oil and butter using the standard baking ratio.Popcorn yieldPopped popcorn volume from a quantity of unpopped kernels, and servings it makes.Grams to cupsConverts a weight of a common baking ingredient to cups, using typical ingredient density.Butter Tablespoons to GramsConverts tablespoons of butter to grams, or grams to tablespoons, both directions.

Sports

Performance and scoring maths for training and competition, from running pace and gear ratios through to rating systems and win percentages.

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Steps to caloriesEstimated calories burned from a step count, body weight and average stride length.Half Marathon PaceRequired pace and split times for a half or full marathon from a target finish time.Average SpeedAverage speed in km/h from total distance and total time, for any mode of travel.Bike gear ratio & speedGear ratio, development and road speed for a given chainring, cog and cadence.Bike frame sizeRecommended frame size from inseam length, by bike type.Stride length & distance from stepsStride length from height, and a step count turned into distance.Hull speed (displacement boat)The theoretical top speed of a displacement-hull boat from its waterline length.Wilks score (powerlifting)Bodyweight-adjusted strength score for comparing lifters across weight classes.Elo rating changeHow a single result moves a player or team’s Elo rating.NFL passer ratingThe 0–158.3 quarterback rating from completions, yards, touchdowns and interceptions.Race time predictorPredicts a finish time at a new distance from a recent race result, using Riegel’s formula.Hiking time (Naismith’s rule)Estimated walking time for a hike from distance and total ascent.Bruce protocol VO₂maxEstimated maximal oxygen uptake from total time on a standard Bruce treadmill test.Magic number (pennant race)Combined wins by your team and losses by the nearest rival needed to clinch a spot.Net run rate (cricket)The run-rate differential used to separate teams level on points.Bench Press PyramidA pyramid set-and-rep scheme for bench press, stepping weight up toward a top set from a target working weight.Follow On in Test Cricket CalculatorChecks whether a lead after the first innings of a Test match meets the 200-run follow-on threshold.Net Run Rate (NRR) CalculatorNet run rate for a cricket team from runs and overs, using the scored-minus-conceded method.Win/Loss Percentage CalculatorWin percentage from wins, losses and optional ties, using either the standard or half-win tie convention.Ski Length CalculatorGeneral starting guide to ski length from height and ability level, using standard chin-to-forehead sizing bands.Bike Sizing CalculatorA general bicycle frame size range from rider height, for road, mountain and hybrid bikes.E-bike rangeEstimated riding range from battery capacity and energy use per distance.Fishing reel line capacityHow much line of a new diameter fits on a reel, from a known spool capacity.Pool table room sizeMinimum room dimensions so a cue has room to swing on every shot.Sauna Calories BurnedA realistic, non-exaggerated estimate of calories burned during a sauna session, from resting metabolic rate.Skipping Rope Calories BurnedCalories burned skipping rope from your weight, session length and pace, using standard MET values.Battery Capacity Unit ConverterConverts battery capacity between mAh, Ah and Wh at a given voltage.Speed (km/h) CalculatorAverage speed in km/h from a distance and time, for running, cycling, driving or boating.Training Pace Zones CalculatorEasy, tempo, threshold and interval pace zones from a recent race time or known baseline pace.Steps to MilesConverts a step count to miles, or a target distance in miles to steps, from an average stride length.Beer Pong Cups CalculatorNumber of cups needed per side and in total for a triangle beer pong rack, for any rack size.Swim pacePace per 100 m/yd and average speed for a swim, from distance and time.Cycling power-to-weightWatts per kilogram from your power output and body weight, with a rough training category.Golf course handicapCourse handicap for a round, from Handicap Index, Slope Rating and Course Rating.Ape indexHow your arm span compares to your height, a rough climbing-reach indicator.Bike Pace CalculatorAverage pace per kilometre or mile and road speed from a distance ridden and the time it took.Arrow Kinetic EnergyKinetic energy and momentum of an arrow from its measured or chronographed speed and weight.Boat Speed (Horsepower) CalculatorRough top-speed estimate for a planing boat from engine horsepower and total weight, using the Crouch formula.FIDE Rating CalculatorFIDE-style Elo rating change after one game, using the published FIDE K-factor rules for player category.Cricket Strike Rate CalculatorBatting strike rate from runs and balls faced, or bowling strike rate from balls bowled and wickets taken.ERA (Earned Run Average) CalculatorA baseball pitcher's earned run average, scaled to a standard 9-inning game.MET CalculatorCalories burned from any MET value you enter, plus body weight and duration.Arrow FOC (Front of Centre) CalculatorFront of centre percentage for an arrow, from its length and balance point measured from the nock.VO2 Max Calculator (Cooper Test)Estimates VO2 max from the distance covered in a 12-minute Cooper test, with the equivalent pace.Bike chain lengthChain length in links for a bike from chainstay length and the largest chainring and cog.Baseball WHIPWalks plus hits per inning pitched, the standard measure of baserunners a pitcher allows.Winning percentageWin rate for a team or player, with ties counted as half a win.Batting average (baseball or cricket)Hitting average from hits and at-bats, or runs and dismissals for cricket.Slugging percentageTotal bases per at-bat, a power-hitting measure in baseball and softball.Goalie save percentageShare of shots faced that a goalkeeper stopped, hockey or soccer.Effective field goal percentage (eFG%)Basketball shooting efficiency that weights three-pointers as worth more.Cricket bowling averageRuns conceded per wicket taken, lower is better for a bowler.Earned run average (ERA)A pitcher’s earned runs allowed per nine innings pitched, baseball or softball.Calories burned by heart rateEnergy burned during exercise from average heart rate, age, weight and sex.Vertical leap needed to dunkMinimum vertical jump required to dunk a basketball, from your standing reach and rim height.Rowing ergometer pace to wattsConverts a rowing machine 500 m split time to power output, the Concept2 formula.Triathlon total timeAdds swim, transition, bike and run splits into a total triathlon finish time.On-base percentage (OBP)How often a batter reaches base safely per plate appearance, baseball or softball.Fielding percentageShare of fielding chances handled cleanly, baseball or softball defense.Bench press one-rep maxEstimated one-rep max (1RM) bench press from a weight and rep count, using the Epley formula.NBA game scoreJohn Hollinger’s single-game performance rating from a box score line.True shooting percentageBasketball shooting efficiency that accounts for three-pointers and free throws.MET-minutes per weekWeekly physical activity volume in MET-minutes, checked against the WHO activity guideline.Goals against average (hockey)A goaltender’s goals allowed per 60 minutes of play, the standard hockey goaltending stat.Cricket batting strike rateRuns scored per 100 balls faced, the standard measure of scoring pace in cricket.Steps to km calculatorConverts a step count to distance, or a target distance to steps, from an average stride length.VO2 max calculator for runnersEstimates VO2 max for a runner from a recent race distance and finish time (Jack Daniels formula).Pace calculatorSolves for pace, time or distance when the other two are known.One-rep max (1RM) estimatorEstimated one-rep max for any lift, from a weight and rep count, across four common formulas.

Chemistry

Concentrations, pH, dilutions, gas laws and reaction yields: the maths behind the lab bench, with every constant and assumption stated.

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Electronegativity CalculatorPauling-scale electronegativity of an element, or the difference between two elements to judge bond polarity.Molarity from massConcentration of a solution made from a known mass of solute.Solution dilution (C₁V₁ = C₂V₂)Stock volume and diluent needed to hit a target concentration.pH from hydrogen ion concentrationConversion between [H⁺] and pH, with pOH and [OH⁻] at 25 °C.Henderson–Hasselbalch (buffer pH)Buffer pH from the acid dissociation constant and the base/acid ratio.Percent yieldHow much product a reaction actually gave versus the theoretical maximum.Mass percent concentrationSolute mass as a percentage of total solution mass, plus ppm.Radioactive decay & half-lifeAmount of a substance remaining after a given elapsed time.Beer–Lambert law (absorbance)Absorbance and transmittance of a solution from its concentration.Osmotic pressure (van’t Hoff)Pressure needed to stop osmosis across a semipermeable membrane.Solubility Rules CalculatorPredicts whether an ionic compound is soluble in water, using the standard solubility rules.Mole CalculatorConverts between mass and moles of a substance using its molar mass.Types of Chemical Reactions ClassifierIdentifies the standard reaction type from the number of reactants and products.Ionic CalculatorThe correct chemical formula of an ionic compound from a chosen cation and anion, by balancing charges.Mole Ratio CalculatorMole ratio between two substances in a balanced reaction, from their equation coefficients or from given mole amounts.Net Ionic Equation CalculatorBalances a double-displacement reaction between two soluble ionic compounds and removes the spectator ions.Theoretical Yield CalculatorMaximum mass of product obtainable from a limiting reagent, using molar masses and the balanced equation ratio.Entropy of ReactionEntropy change of a reaction from the total entropy of its products and reactants.Water Boiling Point (Altitude)How the boiling point of water falls as elevation rises, from the drop in atmospheric pressure.Electron Configuration CalculatorFull electron configuration for any element from atomic number 1 to 56, following the Aufbau principle.Molality of a solutionMoles of solute per kilogram of solvent, a concentration measure independent of temperature.Acid-base titration (equivalence point)Unknown acid or base concentration from the titrant volume at the equivalence point.Freezing point depressionHow much a solvent’s freezing point drops when a solute is dissolved in it (a colligative property).Boiling point elevationHow much a solvent’s boiling point rises when a solute is dissolved in it (a colligative property).Buffer capacity (Van Slyke equation)How resistant a buffer solution is to pH change, from its total concentration and pKa.Arrhenius equationReaction rate constant at a given temperature from activation energy and pre-exponential factor.Mole fraction of a mixtureFraction of the total moles in a mixture contributed by each component.Water hardness (as CaCO₃)Total water hardness as calcium carbonate equivalent, from calcium and magnesium ions.Serial dilution seriesFinal concentration after a series of equal-factor dilutions, and the concentration at each step.Raoult’s law (vapor pressure of a solution)Vapor pressure of an ideal solution containing a non-volatile solute.Mol/L to mg/L CalculatorConverts molar concentration (mol/L) to mass concentration (mg/L) and back, using the molar mass of the substance.Weak acid/base pH from Ka or KbpH of a weak acid or base solution from its dissociation constant and starting concentration.Activation energy from two rate constantsActivation energy from rate constants at two temperatures (two-point Arrhenius equation).Kp ↔ Kc equilibrium constant conversionConvert between pressure-based and concentration-based equilibrium constants for a reaction.Degree of unsaturation (DBE)Number of rings and pi bonds in a molecule from its molecular formula.Empirical formula from mass percentSimplest whole-number atom ratio of a compound from percent composition and atomic masses.Ionic strength of a solutionIonic strength from the concentration and charge of every ion present in a solution.Graham's law of effusion/diffusionRelative rate at which two gases effuse or diffuse, from their molar masses.Radioactive activity (Bq / Ci)Decay rate of a radioactive sample from its amount and half-life, in becquerels and curies.Rate constant from concentration vs. timeReaction rate constant k from concentration data, for zero, first or second order kinetics.Atom economyShare of reactant mass that ends up in the desired product versus all products formed.Average atomic mass from isotopesWeighted average atomic mass of an element from its isotope masses and natural abundances.Molecular Weight CalculatorMolecular weight of a chemical formula, summing standard atomic weights for each element present.Nernst Equation CalculatorCell potential under non-standard conditions from standard potential, temperature, electrons transferred and the reaction quotient.Gibbs free energyReaction spontaneity from the change in enthalpy, entropy and temperature.Partial pressure (Dalton's law)Partial pressure of each gas in a mixture from its moles, volume and temperature.Bond order (MO theory)Bond order and bond stability of a molecule from its bonding and antibonding electron counts.Diffusion coefficient (Stokes-Einstein)Diffusion rate of a spherical particle in a fluid, from its size, viscosity and temperature.Young-Laplace pressure (capillary)Pressure difference across a curved liquid interface, from surface tension and curvature.Isoelectric point (pI)pH at which a molecule such as an amino acid carries no net electric charge.Grams to molesConverts a mass in grams to an amount in moles using the substance’s molar mass.Molar mass of a gasFinds a gas’s molar mass from its mass, pressure, volume and temperature (ideal gas law).Normality of a solutionConverts molarity to normality using the number of equivalents per mole.pKa from KaCalculates pKa from the acid dissociation constant Ka using pKa = -log10(Ka).Alligation mixing ratioFinds the ratio and volumes of two concentrations that mix to a target concentration.Crude protein from nitrogenEstimates crude protein percentage from measured nitrogen content and a conversion factor.PPM to molarityConverts a concentration in ppm (mg/L) to molarity using the solute molar mass.Reaction quotient (Q)Calculates the reaction quotient Q for aA + bB ⇌ cC + dD from current concentrations.Combustion analysisFinds the empirical formula of a CHO compound from the CO2 and H2O produced by combustion.Saponification valueDetermines a fat or oil’s saponification value from a KOH back-titration with HCl.Vapor pressure (Clausius–Clapeyron)Finds vapor pressure at a new temperature from a known point and enthalpy of vaporization.Avogadro's number (particles from moles)Number of particles and sample mass from an amount in moles.Atom composition (protons, neutrons, electrons)Subatomic particle counts from atomic number, mass number and charge.Percent ionic characterIonic character of a bond estimated from the electronegativity difference.Lattice energy (Kapustinskii equation)Ionic crystal lattice energy from ion charges, radii and formula-unit count.Cubic unit cell (packing efficiency)Edge length, atoms per cell and packing efficiency for SC, BCC and FCC lattices.Miller indices from axial interceptsMiller indices (hkl) of a crystal plane, plus interplanar spacing for a cubic lattice.Combustion reaction balancerBalanced coefficients for complete combustion of a CxHyOz compound in oxygen.Stoichiometric air-fuel ratioTheoretical air-to-fuel mass ratio for complete combustion of a CxHy hydrocarbon.STP conversionCorrects a measured gas volume to STP and finds the equivalent moles.Enzyme activity from absorbanceEnzyme activity in units (µmol substrate/min) from an absorbance-vs-time assay.Chemical oxygen demand (COD)COD of a water or wastewater sample from a ferrous ammonium sulfate (FAS) back-titration.Activity coefficient (Debye-Hückel)Ionic activity coefficient of a dissolved ion from its charge and the solution ionic strength.Gibbs' phase ruleDegrees of freedom of a chemical system from its number of components and coexisting phases.Bleach dilution to target strengthBleach and water needed to dilute a stock solution down to a target free-chlorine strength.Percent solution (% w/v)Weight-per-volume percent concentration of a solution from the mass of solute dissolved.Radiocarbon (carbon-14) datingEstimated age of an organic sample from the fraction of carbon-14 remaining.Rate constant from a rate lawReaction rate constant k from a single measured rate and reactant concentrations.Electrolysis mass deposited (Faraday's law)Mass of an element deposited or liberated during electrolysis, from current and time.Resuspension volume/concentrationBuffer volume to resuspend a dried sample to a target concentration, or vice versa.

Biology

Population genetics, enzyme kinetics, growth curves, dosing and lab concentration formulas for students, researchers and animal keepers.

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Hardy–Weinberg equilibriumExpected genotype frequencies in a non-evolving population from allele frequency.DNA/RNA concentration from A₂₆₀Nucleic acid concentration from a spectrophotometer absorbance reading.Log reduction (microbial kill)How many orders of magnitude a treatment reduces a microbial count.Michaelis–Menten kineticsEnzyme reaction rate at a given substrate concentration.Bacterial/cell growth (doubling time)Population size after exponential growth at a fixed doubling time.Q₁₀ temperature coefficientHow much a biological or chemical rate changes per 10 °C rise.Plant water potentialTotal water potential from solute and pressure potential in a plant cell.Can Cats Eat ChocolateTheobromine dose from chocolate eaten, checked against published toxicity thresholds for cats.Onion Toxicity in Dogs CalculatorEstimated onion dose per kg of body weight, checked against published toxicity thresholds.Adult dog weight predictorRough adult weight estimate for a medium or large breed puppy, from its weight at 14-16 weeks.Cattle per Acre CalculatorEstimated stocking density: cattle a given acreage can support, or acres needed per head, from your own assumption.Allele frequency from genotype countsDirect-count allele frequencies for a two-allele gene from observed genotype numbers in a sample.Multi-gene cross probabilityProbability of a given number of recessive traits among offspring of a multi-gene cross.DNA copy number from concentrationDNA or RNA molecules per microlitre from concentration and fragment length.PCR primer melting temperature (Tm)Estimated primer melting temperature from base composition (Wallace/Marmur-Doty).qPCR amplification efficiencyPCR amplification efficiency from the slope of a standard curve (log₁₀ starting quantity vs. Ct).Vapor pressure deficit (VPD)Gap between saturation and actual vapor pressure, the driving force for plant transpiration.Monohybrid Punnett Square CalculatorGenotype and phenotype ratios from a single-gene cross, the classic monohybrid Punnett square.Dog Body Condition CalculatorEstimate a dog's body condition score from rib, waist and abdomen checks, a standard vet screening guide.Daily light integral (DLI)Total photosynthetic light a plant receives per day, from light intensity and photoperiod.Mutation frequencyFraction of a tested population carrying a mutation, reported per cell or organism tested.Growing degree units (GDU)Accumulated heat units driving crop development, from daily high/low temperature and a base.Ligation molar ratio (insert:vector)Insert mass needed for a target insert-to-vector molar ratio in a DNA cloning ligation.Cricket chirp thermometerEstimate air temperature from a cricket’s chirp rate using Dolbear’s law.PCR annealing temperature (Ta)Optimal PCR annealing temperature from primer and product melting temperatures.Feed conversion ratio (FCR)Efficiency of converting feed into body weight gain for livestock or aquaculture.Corn yield estimatorEstimated corn yield in bushels per acre using the ear-count yield component method.Acres per hourField work rate from implement width and travel speed, accounting for overlap.Dry matter basis conversionConverts an as-fed nutrient percentage to a dry-matter basis using moisture content.DNA to mRNA transcriptionmRNA transcript from a DNA template strand using base-pairing rules.Tree height (clinometer method)Tree height from the angle to its top and your distance from it.Tree diameter at breast height (DBH)Trunk diameter and cross-sectional area from a measured circumference.Grain bin storage capacityBushel capacity of a cylindrical grain bin from its dimensions.Fertilizer application rateProduct needed to hit a target nutrient rate given the label percentage.Dihybrid cross ratiosGenotype and phenotype ratios from a cross of two heterozygous two-gene parents.Swine gestation (farrowing date)Expected farrowing date from the breeding date, using the average 114-day sow gestation.Water-soluble fertilizer dosingFertilizer weight needed to reach a target nutrient concentration in a given volume of water.

Ecology

Population and diversity formulas for the field, plus grazing capacity, stocking rate, travel emissions and the carbon standing in a measured tree.

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Logistic population growthPopulation size over time under a fixed carrying capacity (Verhulst model).Shannon diversity indexBiodiversity of a community from species counts.Lotka–Volterra predator–prey ratesInstantaneous population growth rates for a classic predator–prey pair.Kaya identity (CO₂ emissions)Global CO₂ emissions decomposed into population, wealth, energy and carbon factors.Tree basal areaCross-sectional trunk area at breast height (DBH), the standard forestry measure of stand density.Animal mortality ratePercentage of a population lost to death over a period, accounting for births during that period.Livestock stocking rateStocking rate in standard animal units per hectare, against the carrying capacity of the land and the head count it supports.Travel emissionsCarbon dioxide equivalent for a journey from an emission factor you supply, split per person and priced at an offset rate.Tree carbon storageCarbon and carbon dioxide stored in a tree, from its measured size, wood density and carbon fraction rather than a species equation.Wind turbine power outputElectrical power generated by a wind turbine from rotor size, wind speed and efficiency.Hydroelectric power outputPower generated by a dam turbine from head, flow rate and efficiency.

Pets

Sizing, feeding and age-conversion maths for the animals in your household, from crate size and litter use to daily calories and hay by the bale.

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Dog age in human yearsA dog's age converted to a human-equivalent age using the epigenetic-clock formula.Cat age in human yearsA cat's age converted to an equivalent human age using the standard veterinary chart.Pet gestation & due dateExpected birth date range for a common pet or farm animal, from the breeding date.Dog & cat daily caloriesDaily energy needs from resting energy requirement and an activity factor.Dog daily water intakeRoughly how much water a dog needs per day, by activity level.Dog crate sizeMinimum crate dimensions so a dog can stand, turn around and lie stretched out.Turtle tank sizeMinimum water volume for a pet turtle based on shell length.Chicken coop & run sizeMinimum floor space for a flock, depending on how much outdoor access they get.Dog chocolate toxicity riskTheobromine dose from chocolate eaten, checked against published toxicity thresholds.Rabbit cage sizeMinimum enclosure dimensions based on a measured hop, body length and standing height.Dog daily food amountDaily feeding amount as a percentage of body weight, by life stage.Cost of owning a petFirst-year and ongoing costs from your own monthly and one-off figures.Guinea pig & hamster ageHuman-equivalent age for a guinea pig or hamster from published veterinary age charts.Fish tank stockingRoughly how many inches of fish a freshwater community tank can hold.Pet bird ageHuman-equivalent age for a pet bird, scaled by its species’ typical lifespan.Horse weight estimateEstimated adult horse body weight from a heart-girth and body-length tape measurement.Round pen panel countFence panels needed to build a round training pen from its diameter and panel length.Cat litter plannerHow much litter a household gets through in a month, from tray size, depth and how often it is changed, with the bags and the cost.Horse hay requirementDaily hay for a horse as a percentage of bodyweight, adjusted for dry matter and pasture, with bales and cost for a planning period.Dog harness sizeRecommended harness size from chest girth, the measurement harnesses are actually fitted to.Dog heat cycle predictorEstimated stage dates and next heat window from the last cycle's start date.Fish weight estimateEstimated live weight of a fish from its length and girth, without using a scale.

Renewable Energy

Sizing and running-cost maths for solar, batteries and heat pumps: panel count, inverter loading, self-consumption value and payback on real figures.

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Solar System SizingSolar array size and panel count needed for a target daily usage, with optional battery sizing.Heat pump running costYearly cost of heating with a heat pump at a given seasonal efficiency, set against a gas boiler and plain electric resistance heating.Solar self-consumption valueWhat a solar array is worth once exports are paid at a lower rate than imports, and what raising self-consumption is worth.Inverter DC to AC ratioWhether a solar array is oversized for its inverter, and how much power the inverter would hold back at full sun.Home battery arbitrage valueWhat a battery earns by charging at the off-peak rate and discharging at the peak rate, once round-trip losses are paid for.Solar Payback PeriodYears to recoup a solar system's net cost from its annual electricity bill savings.Off-Grid Battery SizingBattery capacity needed to cover a daily energy load for a chosen number of autonomy days.Solar Panel Tilt AngleRule-of-thumb fixed tilt angle from latitude, for year-round, winter or summer weighting.Solar Energy YieldEstimated annual output from a solar array, from its size, sun hours and system efficiency.Battery RuntimeHow long a battery powers a continuous load, from capacity, depth of discharge and wattage.

Gaming

Damage, survivability, drop odds and grind time: the arithmetic behind build choices, weapon comparisons and how long a level will really take.

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Damage per second (DPS)Average sustained damage per second for a weapon or ability, including the share that critical hits contribute.Time to kill (TTK)How many shots a target takes and how long that takes at a given rate of fire, the way shooter players compare weapons.Effective HP from armourTurns an armour rating into a damage reduction percentage and the effective health pool it actually buys you.Speedrun paceCompares your time at a checkpoint against the split you are chasing and projects the finish if the rest of the run holds pace.Gacha pity and pull oddsThe chance of pulling what you are after within a number of pulls, allowing for a hard pity count that guarantees it.Mouse cm per 360The distance you physically move the mouse to turn a full circle, which is the figure that actually transfers between games.XP to next levelHow much experience is left to the next level and how long that is at your current rate of earning.Pokemon statWorks out a final stat from the base stat, IVs, EVs, level and nature, using the formula the games have used since generation 3.Minecraft XP levelsConverts Minecraft experience levels to total experience points and tells you how many points stand between two levels.FPS to frame timeConverts a frame rate to the milliseconds each frame takes, and shows what a monitor at a given refresh rate can actually display.Loot set completionExpected attempts to collect every item in a set when each is equally likely, allowing for duplicates and for attempts that drop nothing.Games to rank upHow many games a climb takes at your win rate, and the win rate you need just to stop sliding backwards.Game backlog completion timeHow long an unplayed pile takes to clear at your playing hours, and whether it is shrinking at all once new purchases are counted.Crafting resource treeHow much raw material a multi-tier recipe swallows, where every tier is crafted from several of the tier below it.Peeker’s advantageThe head start a player gets by moving around a corner first, added up from both players’ latency, the server tick and the interpolation buffer.Damage reduction stackingCombines several percentage damage reductions the way games actually apply them, one after another, and shows what the naive sum gets wrong.

Real Estate

Investment property maths: rule-of-thumb screens, loan-to-value, transfer duty, weekly holding cost and the price a sale must reach to break even.

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Break-even occupancyThe occupancy rate at which rental income exactly covers operating costs and loan repayments, and how many weeks a year you can afford to sit empty.Property holding cost per weekWhat an investment property costs out of pocket each week once rent, interest, vacancy and management fees are all counted.Stamp duty from a bracket scaleProgressive transfer duty worked out from a scale you enter yourself, with the amount falling in each band shown separately.Break-even sale priceWhat a property has to sell for to get your money back once purchase costs, improvements, holding costs and selling fees are all counted.Loan-to-Value (LTV)What share of a property's value is being borrowed, the core metric lenders use to size risk.Debt Yield RatioNet operating income as a share of the loan amount, a lender risk check on the loan size.Price per Square FootPurchase price divided by floor area, plus the implied price at a target rate per sq ft.1% Rule ScreenerChecks monthly rent as a percentage of price against the commonly cited 1% screening threshold.House Flip ROIProfit and return on cash invested for a fix-and-flip project, ARV to selling costs.BRRRR Cash-on-Cash ReturnCash left in a Buy, Rehab, Rent, Refinance, Repeat deal after refinancing, and its return.Vacancy RateVacant unit-days as a share of total available unit-days across a rental property or portfolio.

Photography

The maths behind exposure, depth of field, ND filters, time-lapse intervals, star trails, shutter angle and the storage a shoot will actually need.

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ND filter exposureThe shutter speed a neutral density filter needs, from a filter labelled in stops, as an ND number or as an optical density.Time-lapse intervalHow long a time-lapse clip runs from the shooting interval, how many frames it takes and how much card space they need.500 rule for star photographyThe longest exposure before stars trail, from focal length and crop factor, with a stricter divisor and a declination allowance.Shutter angle to shutter speedConverts a cine shutter angle to a shutter speed at any frame rate, and finds the angle that matches a shutter speed you want.Depth of FieldNear and far sharpness limits from focal length, aperture, sensor format and subject distance.Exposure EquivalentThe matching change needed in a second setting to hold exposure equivalent after changing one.Print Resolution (DPI)Resulting DPI for a print size, or the maximum print size for a target DPI.Video File SizeVideo file size in megabytes and gigabytes from bitrate and duration.Photo Shoot StorageTotal storage needed for a shoot from photo count, photo size and video minutes.Crop Factor Equivalent Focal LengthFull-frame-equivalent focal length for a lens used on a cropped-sensor camera.

HR & Workforce

Staffing and workforce maths: full-time equivalents, turnover, leave accrual, cost per hire, total employment cost and the funnel behind a vacancy.

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Cost per hireRecruiting spend divided by the hires it produced, split between external and internal costs and set against the salary being filled.Revenue per employeeRevenue divided by full-time equivalent staff, with the employment cost behind it and the share of revenue that labour consumes.Bradford factorThe absence score that weights frequent short spells far more heavily than one long one, with the days needed to reach a trigger point.Total employment costWhat an employee costs once retirement contributions, payroll tax, insurance and fixed per-head costs are added to the base salary.Recruitment funnelHow many applications a vacancy needs, worked backwards from the hires wanted through offer, interview and screening conversion rates.FTE (Full-Time Equivalent)Full-time equivalent headcount from a mix of full-time and part-time staff hours.Employee Turnover RateTurnover rate from separations and average headcount over a period.Overtime PayTotal pay from regular and overtime hours at a chosen overtime multiplier.PTO Accrual RatePTO hours accrued per pay period and running balance after periods worked.Staffing RatioStaff-to-units ratio and its inverse, for any service where staff cover units served.

Insurance

Coverage-sizing maths for life, income protection, property and business insurance: how much cover you need, and what underinsurance costs at claim time.

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Rebuild cost sum insuredWhat it would cost to rebuild a home from scratch, including demolition, professional fees and cost rises during the build, rather than what it would sell for.Coinsurance penaltyHow much a claim is cut when the sum insured falls short of the coinsurance requirement, and the sum insured that would avoid any reduction.Income protection coverThe monthly benefit an income protection policy would pay, set against essential expenses, with the savings needed to bridge the waiting period.Business interruption coverThe sum insured a business interruption policy needs, from gross profit, the indemnity period and an allowance for growth while the claim runs.Life Insurance Needs (DIME Method)Rough coverage estimate from debts, income replacement, mortgage and education costs.Premium Per $1,000 of CoverageAnnual premium rate per $1,000 of coverage, for comparing quotes of different sizes.Deductible vs Premium Break-EvenYears of premium savings needed to offset paying a higher deductible once.Umbrella Policy Coverage GapGap between a target liability protection level and existing auto and home liability limits.Human Life Value MethodPresent value of future net income, an actuarial approach to sizing life insurance.

Aviation

Airspeed, wind, fuel burn, density altitude and weight and balance, plus descent planning, climb gradient and engine-out glide range for pilots.

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Top of descentHow far out to start down for a given descent angle, with the rate of descent and the time it takes.Wind correction angleThe heading to fly to hold a track in a crosswind, with the groundspeed that results and the time for a given leg.Climb gradientConverts a rate of climb and groundspeed into a climb gradient in feet per nautical mile, and checks it against a required departure gradient.Glide distanceHow far an aircraft glides from a given height at its best glide ratio, adjusted for a headwind or tailwind, and the height needed to reach a field.True Airspeed EstimateQuick true airspeed estimate from indicated airspeed and altitude, the pilot rule of thumb.Runway Crosswind & Headwind ComponentSplits wind into crosswind and headwind/tailwind for a given runway heading and wind direction.Fuel Burn Endurance & RangeFlight endurance and still-air range from usable fuel, burn rate and cruise speed.Density Altitude EstimateQuick density altitude estimate from pressure altitude and outside air temperature.Weight & Balance (Centre of Gravity)Total weight and centre of gravity from up to four weight-and-arm stations.

3D Printing

Filament use, resin cost, print time and scaling maths for FDM and resin printing, plus hotend flow limits and extruder step calibration.

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Maximum volumetric speedThe volumetric flow a print setting demands in cubic millimetres per second, and the fastest print speed the hotend can actually feed.Resin print costWhat a resin print costs in material, allowing for supports, a failure rate and the price of a bottle.Extruder steps per mmCorrected extruder steps per millimetre from a measured extrusion test, with the error it removes.Filament Weight & CostEstimated filament weight and cost for a print, from model volume, material and infill.Print Time EstimateRough print time from total filament length needed and the printer feed rate.Layer Count & Solid Shell LayersPrint layer count from model height, and solid layers needed for a target shell thickness.Infill Volume & WeightEffective print volume from shell volume, interior volume and infill percentage.Shrinkage Compensation ScalingScale factor to apply in the slicer so a printed part comes out at the intended size.

SEO

Keyword density, meta-tag length, backlink ratios, readability scoring and what an organic ranking is worth against the price of the same clicks.

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Keyword traffic valueWhat the clicks from a keyword would cost to buy in paid search, and what they are worth once conversion rate and order value are applied.Readability scoreFlesch Reading Ease, Flesch-Kincaid grade level and Gunning Fog for a passage of text, with the word, sentence and syllable counts behind them.Keyword DensityHow much of a page's word count is made up of one target keyword or phrase.Title Tag Length CheckerCharacter and approximate pixel width of a page title against Google's search-result guideline.Meta Description Length CheckerCharacter count of a meta description against the guideline before search results truncate it.Dofollow vs Nofollow Backlink RatioThe split between dofollow and nofollow backlinks, as a ratio and as a share of the total.Core Web Vitals CheckerRates LCP, INP and CLS against Google's published Good, Needs Improvement and Poor thresholds.Text-to-HTML RatioThe share of a page's total weight that is visible text, versus markup, scripts and styling.Anchor Text DiversityThe share of inbound anchor text that is exact-match, partial-match or branded/generic.

Marketing

The core paid-media metrics: CPM, CPC, CPA, CTR, ROAS and more, each with the formula shown and worked examples.

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CPM (Cost Per Mille)Cost per 1,000 ad impressions, and the impressions or budget that go with it.CPC (Cost Per Click)Average cost per click from total spend and clicks, the core paid-search and paid-social metric.CTR (Click-Through Rate)Share of impressions that turned into a click, the standard measure of ad relevance.CPA (Cost Per Acquisition)Average spend needed to win one paying customer or completed sale.Conversion RateShare of visitors or clicks that completed the goal action, such as a purchase or sign-up.ROAS (Return On Ad Spend)Revenue earned for every dollar of ad spend, and the equivalent ROI percentage.CPL (Cost Per Lead)Average spend needed to generate one lead, before that lead becomes a paying customer.CPV (Cost Per View)Average cost per video view, the key metric for video and YouTube ad campaigns.CPI (Cost Per Install)Average spend needed to acquire one app install, the core mobile user-acquisition metric.Reach & FrequencyUnique people reached and average number of times each saw the ad, from total impressions.Break-Even ROASThe minimum ROAS an ad campaign needs to hit, from your profit margin, and the matching target CPA.

E-commerce

Order economics and inventory maths for online and retail sellers: average order value, customer lifetime value, reorder points and break-even.

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Average Order Value (AOV)Average revenue per order, from total revenue and number of orders.E-commerce Customer Lifetime ValueCustomer value from average order value, orders per year and years as a customer.Inventory Reorder PointStock level at which to reorder, from daily usage, lead time and safety stock.Safety Stock CalculatorBuffer stock needed to cover demand variability at a chosen service level.Shipping Cost Per UnitAverage shipping cost per unit, from total shipping spend and units shipped.E-commerce Break-Even UnitsUnits and revenue needed to cover fixed costs, from price and variable cost per unit.Cart Abandonment RateShare of carts created that did not end in a completed purchase.