Fill in any row. Each answer shows the formula it used.
What is X% of Y?
X is what percent of Y?
Percentage change from A to B
Increase or decrease a number by a percentage
X is Y% of what? (reverse percentage)
How to use it
Each box answers one common question. Type two numbers and the result appears at once, with the formula underneath so you can check it or copy it into a spreadsheet.
X% of Y: 15% of 80 = 15 ÷ 100 × 80 = 12.
What percent: 12 is 12 ÷ 80 × 100 = 15% of 80.
Percentage change: from 80 to 100 is (100 − 80) ÷ 80 × 100 = +25%. Going back from 100 to 80 is −20%, not −25%, because the starting value changed.
Increase/decrease: 80 plus 25% = 80 × 1.25 = 100. A 20% discount on 100 = 100 × 0.8 = 80.
Reverse percentage: if 12 is 15% of a number, the number is 12 ÷ 0.15 = 80. Use this to find a price before VAT or before a discount.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. 20% of 150 is 0.2 × 150 = 30.
What is the difference between percent and percentage points?
If a rate goes from 10% to 12%, it rose by 2 percentage points, which is a 20% increase in the rate itself.
How do I remove VAT from a price?
Use the reverse percentage row. A price including 20% VAT is 120% of the net price, so divide by 1.2.