% Percentage Calculator
Calculate percentages, percentage change, and percentage of a number. Quick and easy percentage math.
What is X% of Y?
X is what % of Y?
% change from X to Y
About the Percentage Calculator
This percentage calculator runs entirely in your browser and helps with the three most common percentage calculations. Enter your numbers, click Calculate, and the result appears instantly. No data is sent anywhere — every calculation is performed locally with JavaScript.
Common percentage formulas
- What is X% of Y? — Multiply Y by X divided by 100:
(X / 100) × Y. Example: 20% of 50 = (20 / 100) × 50 = 10. - X is what % of Y? — Divide X by Y and multiply by 100:
(X / Y) × 100. Example: 10 is what % of 50 = (10 / 50) × 100 = 20%. - % change from X to Y — Subtract X from Y, divide by X, multiply by 100:
((Y − X) / X) × 100. A positive result is an increase, a negative one is a decrease.
How to use the calculator
- Find the card that matches your question.
- Type your numbers into the input fields.
- Click Calculate to see the result in bold text below the button.
- Repeat for any of the three modes — each one works independently.
Frequently asked questions
Why does the percentage change show a negative number? A negative result means the value decreased from X to Y. A positive result means it increased.
What happens if I divide by zero? The calculator shows an error message because division by zero is undefined. Make sure the divisor (Y for mode 2, X for mode 3) is not zero.
Can I use decimals? Yes. All three modes accept decimal numbers and produce results rounded to two decimal places.
Is my input stored or uploaded? No. Everything happens in your browser. Your numbers are never sent to a server.