A reference desk of calculators that print the equation they evaluate, explain every input, and take each rate and assumption from you rather than burying a figure that will be out of date next year.
The calculators people open most often.
Every category, grouped. Each one lists its full set.
Loans, mortgages, valuations, business ratios and growth metrics: the maths behind money decisions, with every rate a field you set yourself.
Body composition, training load, nutrition and sports performance, worked out with published clinical and sports-science formulas, each one named.
Algebra, trigonometry, geometry and statistics, with the working shown beside every answer so you can check the method rather than trust the result.
Unit conversion, home and trade quantities, cooking, pets and photography: the practical calculations that daily life actually runs on.
Everything measured in days and hours: ages, durations, business days, countdowns and timesheets, on real calendar arithmetic.
Physics, chemistry, biology, ecology and renewable energy: first-principles formulas for the lab bench, the field and the classroom.
Three rules the whole site follows.
Most calculators quietly bake in a tax rate, a fuel price or a contribution cap, and are wrong the day it changes. Here every rate, price and threshold is a field you set yourself.
Each tool prints the equation it evaluates and explains what every input means, so you can check the answer by hand or rebuild it in a spreadsheet.
The example tables are generated by running the calculator itself at build time. The numbers in the prose cannot drift from the tool, because they come from it.
Short pieces on the arithmetic, and where it usually goes wrong.