Percentage Calculator
Three of the most common percentage questions, each solved as you type.
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The three formulas
| Question | Formula | Example |
|---|---|---|
| X% of a number | (X ÷ 100) × N | 15% of 80 = 12 |
| Part as a % of whole | (part ÷ whole) × 100 | 30 of 120 = 25% |
| % change | ((new − old) ÷ old) × 100 | 200 → 250 = +25% |
Two things people get wrong
Percentage changes do not reverse. A 25% increase then a 25% decrease does not return to the start: 100 → 125 → 93.75. To undo a 25% rise you need a 20% fall.
Stacked discounts multiply. "30% off, then 20% off" is 0.70 × 0.80 = 0.56, so 44% off — not 50%. The same logic applies to compound interest and successive markups.
For converting between units rather than percentages, see the unit conversions cheat sheet.
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Frequently asked questions
How do I find X% of a number?
Divide the percentage by 100 and multiply by the number. 15% of 80 is 0.15 × 80 = 12. In the first box below, enter 15 and 80.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. 30 out of 120 is 30 ÷ 120 × 100 = 25%. Use the second box.
How do I calculate a percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, and multiply by 100. From 200 to 250 is (250 − 200) ÷ 200 × 100 = +25%. From 250 to 200 is −20%. Use the third box. Note that a 25% rise followed by a 20% fall returns you to the start — percentage changes are not symmetric.
What is the difference between percentage points and percent?
If a rate goes from 4% to 6%, that is a rise of 2 percentage points but a 50% increase (2 ÷ 4). News reports often confuse the two. Use 'percentage points' for the arithmetic difference between two percentages and 'percent' for the relative change.
How do I add or remove sales tax / VAT with a percentage?
To add 8% tax to $50: 50 × 1.08 = $54. To find the pre-tax price from a $54 total that includes 8% tax: 54 ÷ 1.08 = $50 — divide by 1 plus the rate, do not subtract 8%.
How do I calculate a tip?
Multiply the bill by the tip rate as a decimal. A 20% tip on $46 is 46 × 0.20 = $9.20, for a $55.20 total. To split it, divide the total by the number of people.
What is a percentage of a percentage?
Multiply the two decimals. 50% of 20% is 0.5 × 0.2 = 0.1 = 10%. This comes up with stacked discounts: '30% off, then an extra 20% off' is 0.7 × 0.8 = 0.56, so 44% off, not 50%.
Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.