Calculators that stay on your device

These calculators answer the small questions that show up while shopping or splitting a bill. Each page states the rule before it shows a number.

Body mass index and the Mifflin–St Jeor estimate are screening figures for adults. They do not diagnose anything and they do not replace a clinician.

These pages show how compound growth and a fixed installment are calculated. They leave out fees, taxes, and insurance on purpose.

Both calculators use civil dates and count whole days in UTC, so a time zone cannot change the result. The age page states what happens to a 29 February birthday.

Length and weight use exact international definitions. Temperature uses the usual Celsius, Fahrenheit, and kelvin relations. There is no currency conversion.

Completed age on a chosen date, including what happens on 29 February.

Adult BMI from metric or imperial measures, with the screening ranges named.

Mifflin–St Jeor BMR, then a clearly labeled activity multiplier for a daily estimate.

Compound growth with contributions, a year-by-year table, and a simple chart.

The span between two dates in days, weeks, and calendar months.

Stacked discounts applied one after another, not added into one percent.

The fixed installment on a fully amortizing loan, plus a basic repayment table.

Three everyday percentage questions, with the arithmetic written out.

A tip on a bill, then an equal split, with rounding called out.

Length, weight, and temperature, using exact international definitions.