Percentage Calculator
Four common percentage calculations in one tool: find a percentage of a number, find what percent one number is of another, calculate percent increase/decrease, or find the original number.
Result
—
Calculated locally. Your numbers never leave your browser.
Common questions
What's the difference between this and the standalone Percentage Change and Percentage Difference calculators?
This tool bundles four common modes in one place — percentage of a number, what-percent-of, percent increase/decrease, and find-the-original-number — and shares its underlying math with those two standalone tools. If you specifically need percent change (with its before/after order and sign convention) or percent difference (order-independent), the dedicated calculators walk through those cases in more depth.
Why does it reject 0 in some fields, like the starting value or the percentage?
Percent increase/decrease divides by the starting number, and find-the-original divides by the percentage — in both cases, dividing by zero has no defined result, so it's rejected with a clear message rather than silently returning 0% or an error that looks like a bug.