Percentage Calculator
Three modes, one tool: find a percentage of a number, work out what percent one number is of another, or measure the percentage change between two values.
Visual
How it works
X% of Y: multiplies Y by X ÷ 100.
X is what % of Y: divides X by Y and multiplies by 100.
% change X → Y: takes the difference (Y − X), divides by the starting value X, and multiplies by 100. A positive result is an increase; a negative result is a decrease.
Frequently asked questions
What is 10% of a number, quickly?
Move the decimal point one place to the left. 10% of 240 is 24. From there, 20% is double that, 5% is half that, and so on.
Why does % change use the old value as the base?
Change is measured relative to where you started. Going from 50 to 75 is +50% (25 ÷ 50), while going from 75 back to 50 is −33.3% (−25 ÷ 75) — the same absolute move, different bases.
Can I share my exact calculation?
Yes. Your mode and both numbers are stored in the URL as query parameters, so copying the address bar shares the exact state of the tool.