How to calculate a percentage
To take 15% of 80, multiply 80 by 15 and divide by 100: you get 12. To find what percentage 18 is out of 24, divide 18 by 24 and multiply by 100: 75%.
Updated November 6, 2026 · Sources
Taking a percentage of a number
X% of Y = Y × X ÷ 100. Example: 15% of 80 = 80 × 15 ÷ 100 = 12.
The % sign simply stands for 0.01: 15% of 80 is also 80 × 15 × 0.01.
| Percentage | Result |
|---|---|
| 1 % | 2 |
| 5 % | 10 |
| 10 % | 20 |
| 15 % | 30 |
| 20 % | 40 |
| 25 % | 50 |
| 50 % | 100 |
| 75 % | 150 |
Finding what percentage a part is
Part as % = part ÷ total × 100. Example: 18 right answers out of 24 is 18 ÷ 24 × 100 = 75%.
Adding or removing a percentage
To add 20%, multiply by 1.2: 50 × 1.2 = 60.
To remove 30% (a discount), multiply by 0.7: 80 × 0.7 = 56.
The trap: finding the price before an increase
A price of 120 including a 20% tax is not 96 before tax. Divide by 1.2: 120 ÷ 1.2 = 100.
Removing 20% from 120 takes 20% of the taxed price, while the tax was calculated on the price before tax.