Math Calculators

Percentages and fractions are the arithmetic people look up most, and they are also the two that go wrong most often — usually because the wrong question was asked, not because the sum was hard. Working out 15% of a number, working out what percentage one number is of another, and working out what a number grew by are three different calculations with three different formulas.

Each calculator here separates those cases explicitly rather than making you guess which one you need, and shows the formula and the working underneath so you can check it or learn the method.