How to calculate a percentage of a number
X% of Y = Y × X ÷ 100
15% of 80 is 80 × 15 ÷ 100 = 12. A shortcut: 10% is the number with the decimal moved one place left, so 10% of 80 is 8, and 5% is half that, 4. Add them for 15%: 12.
How to find what percent one number is of another
Percent = part ÷ whole × 100
If 30 of your 120 sales last week were gift cards: 30 ÷ 120 × 100 = 25%.
How to calculate a discount
Sale price = price × (1 − discount ÷ 100)
25% off $60 is 60 × 0.75 = $45, a saving of $15. Two discounts in a row multiply rather than add: 20% off and then another 10% off is 0.8 × 0.9 = 0.72, a 28% discount, not 30%.
Common percentages as fractions
| Percent | Fraction | Decimal |
|---|---|---|
| 10% | 1/10 | 0.1 |
| 20% | 1/5 | 0.2 |
| 25% | 1/4 | 0.25 |
| 33⅓% | 1/3 | 0.333 |
| 50% | 1/2 | 0.5 |
| 75% | 3/4 | 0.75 |
More percentage tools
For a change from one number to another, use the percent change calculator. For tax on a sale, use the sales tax calculator.
Frequently asked questions
How do I work out a percentage of a number?
Multiply the number by the percentage and divide by 100. 15% of $80 is 80 × 15 ÷ 100 = $12.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. $30 out of $120 is 30 ÷ 120 × 100 = 25%.
How do I calculate a discount?
Multiply the price by the discount percentage to get the saving, then subtract it. 25% off $60 is a $15 saving, so $45.