All Calculators

The full index, organised by category.

Every calculator on the site, grouped by category. Each one is free, works in your browser, and explains the formula it uses.

Health & Fitness (21)

Body composition, energy requirements, training zones and the everyday health numbers people actually look up — with the limits of each formula stated plainly.

Finance & Money (14)

Loans, savings, interest, salary and the arithmetic of everyday money decisions, worked through step by step rather than hidden behind a black box.

Maths & Numbers (12)

Percentages, ratios, averages, geometry and algebra, each with the method written out so you can reproduce the answer without the calculator.

Date & Time (5)

Ages, durations, deadlines, working days and time zones — the calculations that are deceptively easy to get wrong by one day.

Unit Conversion (7)

Exact conversions between metric and imperial units, with the definitions and conversion factors the numbers come from.

Home & Everyday (7)

Practical calculations for the house, the car, the kitchen and the shop — quantities, costs and the comparisons that save money.