Percentage calculator
The three percentage questions people actually ask, each with its own boxes. Answers update as you type.
All calculations happen in your browser. Nothing you enter is saved or sent anywhere. See the privacy page.
What is X% of Y?
X is what percent of Y?
Percentage change from X to Y
Questions people ask
What are the three formulas?
X% of Y = X ÷ 100 × Y, so 15% of 200 is 30.
X is what percent of Y = X ÷ Y × 100, so 30 out of 200 is 15%.
change = (new − old) ÷ |old| × 100, so 200 to 250 is +25%.
Why does a 20% fall then a 20% rise not get me back?
Because each percentage is taken from a different starting number. 100 falls 20% to 80, then 80 rises 20% of 80, which is 16, giving 96. To undo a 20% fall you need a 25% rise. The bigger the fall, the bigger the rise needed.
What happens if I start from zero or a negative number?
Percentage change from zero has no meaning, since there is nothing to compare against, so the answer is left blank. Starting from a negative number, the change is measured against the size of that number ignoring its sign: −100 to −50 is a +50% change.