What this calculator does
A calorie deficit calculator works out how many calories a day you can eat to lose weight at a pace you choose, rather than guessing at a round number like 1,500. It starts from your maintenance calories, known as TDEE, then subtracts a deficit sized to a target weekly weight loss, so the number on screen is tied to an actual rate of change rather than a generic diet figure.
A calorie deficit just means eating less than your body burns in a day, so it has to draw on stored energy to make up the difference. Roughly 7,700 kcal of deficit corresponds to about 1 kg of body fat, which is the constant this calculator uses to turn a weekly loss target into a daily number.
The formula
Basal metabolic rate is estimated with the Mifflin-St Jeor equation, then scaled by an activity factor to get TDEE, the same maintenance-calorie estimate used across this site. The target weekly weight loss is converted to a daily deficit by multiplying by 7,700 kcal per kilogram and dividing by 7, then subtracted from TDEE to get the daily calorie target.
| Term | Meaning |
|---|---|
| TDEE | Total daily energy expenditure: the calories burned in an average day at your current weight and activity level, before any deficit is applied. |
| Deficit | The gap between TDEE and calories eaten. A larger deficit produces faster weight loss, up to a point where it becomes hard to sustain or unsafe. |
| 7,700 kcal per kg | The commonly used energy value of a kilogram of body fat, used here to convert a weight-loss rate into a daily calorie number. |
The inputs explained
| Field | What to enter |
|---|---|
| Weight (kg) | Current body weight. |
| Height (cm) | Height without shoes. |
| Age (years) | Age in years. |
| Sex | Biological sex, used because the BMR formula differs slightly between men and women. |
| Activity level | How active a typical week is outside of deliberate weight loss, not including the diet itself. |
| Target weekly weight loss (kg/week) | How much weight you want to lose per week. A common, more sustainable range is 0.25 to 0.5 kg per week; anything much beyond about 1 kg per week is a steep deficit for most people to hold for long. |
When to use it
Picking a realistic weekly target
Choosing a weekly loss rate up front, rather than an arbitrary daily calorie number, keeps the deficit connected to something concrete: a faster target produces a bigger, harder-to-sustain daily gap, which this calculator makes visible before you commit to it.
Checking a deficit against how to calculate calorie deficit by hand
The same arithmetic, TDEE minus a weekly-loss-based deficit, can be done on paper once you know your TDEE, but doing it here also flags when the resulting target looks unusually low for your size.
Adjusting after a plateau
If weight loss stalls, recalculating TDEE at the current, lower body weight (since a lighter body burns somewhat fewer calories) shows whether the same deficit target has quietly become a smaller one in practice.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the daily calorie target changes with a faster weekly weight-loss rate
The same person, at a range of target weekly weight-loss rates.
| Target weekly loss | Daily calorie target | Daily deficit | Deficit as % of TDEE |
|---|---|---|---|
| 0.25 kg/week | 2,358 kcal/day | 275 kcal/day | 10.4% |
| 0.5 kg/week | 2,083 kcal/day | 550 kcal/day | 20.9% |
| 0.75 kg/week | 1,808 kcal/day | 825 kcal/day | 31.3% |
| 1 kg/week | 1,533 kcal/day | 1,100 kcal/day | 41.8% |
| 1.25 kg/week | 1,258 kcal/day | 1,375 kcal/day | 52.2% |
| 1.5 kg/week | 983 kcal/day | 1,650 kcal/day | 62.7% |
How the calorie target changes with activity level, at the same weight-loss goal
The same weight-loss target, across the five activity levels.
| Activity level | Daily calorie target | TDEE (maintenance calories) |
|---|---|---|
| Sedentary | 1,489 kcal/day | 2,039 kcal/day |
| Light | 1,786 kcal/day | 2,336 kcal/day |
| Moderate | 2,083 kcal/day | 2,633 kcal/day |
| Active | 2,380 kcal/day | 2,930 kcal/day |
| Very active | 2,678 kcal/day | 3,228 kcal/day |
Questions
What is a calorie deficit?
It is the gap between the calories your body burns in a day and the calories you eat. Running a consistent deficit forces the body to draw on stored energy, mostly fat, to make up the shortfall, which is what produces weight loss over time.
How is calorie deficit calculated here?
TDEE is estimated from weight, height, age, sex and activity level, then a daily deficit is worked out from your target weekly weight-loss rate using 7,700 kcal per kilogram. Subtracting that deficit from TDEE gives the daily calorie target.
Is a bigger deficit always better?
No. A very large deficit is harder to sustain, can cost muscle along with fat, and tends to be followed by regaining the weight once normal eating resumes. A moderate, steady deficit held consistently usually beats an aggressive one abandoned after a few weeks.
Why does this calculator flag some results?
If the deficit is unusually large relative to TDEE, or the resulting calorie target looks low for typical needs, the calculator notes that it is worth checking against your own circumstances, or with a doctor or dietitian, rather than following it blind.
For the maintenance-calorie figure this deficit is subtracted from, see the TDEE calculator. To turn a calorie target into grams of protein, carbohydrate and fat, use the macronutrient split calculator.