Percentage Calculator
A percentage of a number is the number times the percent divided by 100: 15% of 200 is 200 × 15 ÷ 100 = 30. To find what percent a part is of a whole, divide the part by the whole and multiply by 100.
15% of 200
30
The three percentage formulas
- Percent of a number: number × percent ÷ 100. 15% of 200 = 30.
- What percent X is of Y: X ÷ Y × 100. 30 out of 200 = 15%.
- Percent change: (new − old) ÷ old × 100. From 80 to 100 = +25%.
Percent change is not symmetric
A rise from 80 to 100 is +25%, but the fall from 100 back to 80 is −20%, because the base changes. The same trap shows up with discounts and price hikes: a 50% loss needs a 100% gain to get back to where you started.
Percent vs. percentage points
When a rate moves from 4% to 5%, it rose by 1 percentage point, which is a 25% increase in the rate itself. News reports often mix the two. Use percentage points for the difference between two rates and percent for the relative change.
| Question | Answer |
|---|---|
| 20% of 85 | 17 |
| 42 is what percent of 56? | 75% |
| Change from 120 to 150 | +25% |
| 64 increased by 12.5% | 72 |