About Math calculators
Everyday arithmetic that is easy to get wrong in your head: a percentage of a number, what percent one value is of another, the change between two values, and working backwards from a percentage to the original figure. Each answer comes with the question restated, so you can check that the tool solved the problem you actually had.
The formulas are the standard ones taught in school — divide, multiply by 100, apply the rate to the base — and the engines carry unit tests against hand-worked examples. Nothing you type is stored or sent anywhere, so prices, salaries and grades stay private.
Frequently asked questions
Which percentage formula does this use?
The standard ones: part ÷ whole × 100 for a percentage, and (new − old) ÷ old × 100 for a change. Each mode restates the question above the answer so you can confirm it matches what you meant to ask.
Is my data uploaded?
No. All arithmetic happens in your browser, and the numbers disappear when you close the page.