How to use the percentage calculator
Pick the calculator that matches your question and type your numbers. Results update as you type, and the formula is shown underneath so you can check the math or learn how it works.
Percentage formulas
- X% of Y = X ÷ 100 × Y. Example: 20% of 150 = 30.
- X is what % of Y = X ÷ Y × 100. Example: 30 is 25% of 120.
- Percentage change = (new − old) ÷ old × 100. Example: from 80 to 100 is a 25% increase.
- Add a percentage = Y × (1 + X ÷ 100). Subtract = Y × (1 − X ÷ 100).
Everyday examples
- Discounts: a $50 item with 15% off costs 50 − 15% = $42.50.
- Tips: an 18% tip on a $64 bill is 18% of 64 = $11.52.
- Tax: a price of €120 plus 20% VAT is 120 + 20% = €144.
- Test scores: 42 correct answers out of 50 is 84%.
- Salary or price changes: rent going from 1,200 to 1,290 is a 7.5% increase.
FAQ
Why doesn’t a 50% increase followed by a 50% decrease bring me back to the start?
Because the second percentage is taken of a larger number. 100 + 50% = 150, but 150 − 50% = 75. To undo a 50% increase you need a 33.3% decrease.
What is the difference between percent and percentage points?
If an interest rate goes from 4% to 5%, it rose by 1 percentage point, but by 25 percent (because 1 is 25% of 4).