Percentage calculator
What is X% of Y, X is what percent of Y, and the percentage change from X to Y, with the formula shown.
Result
Percentages come up in three shapes. "What is 15% of 200?" multiplies: 0.15 × 200 = 30. "30 is what percent of 200?" divides: 30 ÷ 200 × 100 = 15%. "From 200 to 230, what is the change?" compares: (230 − 200) ÷ 200 × 100 = +15%. Pick the question, enter the two numbers and the answer appears with the formula written out so you can reuse it.
The change formula divides by the absolute value of the starting number, so a fall from 200 to 150 shows −25% and a rise from −50 to −25 shows +50%. When the starting value is zero the change is undefined and the tool says so rather than showing infinity.
Results keep up to two decimals for money-like inputs and four for percentages. Nothing is rounded before the final step, so 33.33% of 300 gives 99.99, not 100.
How to use it
- Choose the question: X% of Y, X is what % of Y, or change from X to Y.
- Enter X and Y. Negative numbers are allowed.
- Read the answer and the formula line; copy it if you need to show your working.
Frequently asked questions
How do I calculate a percentage increase?
Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 100: (100 − 80) ÷ 80 × 100 = 25%. Choose "Percentage change" and enter 80 and 100.
What is the difference between percentage points and percent?
Going from 10% to 15% is a rise of 5 percentage points but a 50% increase in the rate. This tool reports the relative change (50%); subtract the two figures yourself for percentage points.
Why does a 20% discount followed by a 20% increase not return to the start?
Because the second percentage is taken of a smaller base. 100 − 20% = 80; 80 + 20% = 96. Use the change mode with 100 and 96 to see the net −4%.
Can I compute a percentage of a percentage?
Yes. "What is 50% of 30?" gives 15, which is 15% if the 30 was itself a percentage. The tool treats inputs as plain numbers.
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