Percentage calculator
To find X% of a number, multiply the number by X and divide by 100: 20% of 50 = 50 × 20 ÷ 100 = 10. The three calculators below cover the most common percentage questions.
- Checked on thousands of cases
- Updated November 1, 2026
Percentage of a number
What is % of ?
What percent?
is what percent of ?
Add or subtract a percentage
%
Quick challenge
Streak 0Best 0
Test yourself: every answer is computed by the tool, and the wrong choices are the most common traps.
How it works
Formula: X% of Y = Y × X ÷ 100
A percentage is a number out of 100. To take X% of a value, multiply by X ÷ 100. To find what percent a part is of a whole, divide the part by the whole and multiply by 100. To increase a value by X%, multiply it by (1 + X ÷ 100); to decrease it, multiply by (1 − X ÷ 100). Note that a 20% increase followed by a 20% decrease does not bring you back to the start: 100 → 120 → 96.
Worked examples
30% off $80
30% of 80 = 80 × 30 ÷ 100 = $24. You pay $56.
18 right answers out of 24
18 ÷ 24 × 100 = a 75% score.
Add 20% to $50
50 × (1 + 20 ÷ 100) = $60.
Common mistakes
Taking the percentage off as a number: 80 − 30 = 50.
You take off 30% of the price, not $30: 80 − 24 = 56.
Dividing the wrong way: 24 ÷ 18 × 100 = 133.3%.
The part goes on top, the whole below: 18 ÷ 24 × 100 = 75%.
Thinking +20% then −20% gets you back.
50 → 60 → 48: the cut applies to a bigger amount.
Common percentages
| % | of 50 | of 100 | of 200 | of 1,000 |
|---|---|---|---|---|
| 1% | 0.5 | 1 | 2 | 10 |
| 5% | 2.5 | 5 | 10 | 50 |
| 10% | 5 | 10 | 20 | 100 |
| 15% | 7.5 | 15 | 30 | 150 |
| 20% | 10 | 20 | 40 | 200 |
| 25% | 12.5 | 25 | 50 | 250 |
| 30% | 15 | 30 | 60 | 300 |
| 40% | 20 | 40 | 80 | 400 |
| 50% | 25 | 50 | 100 | 500 |
| 75% | 37.5 | 75 | 150 | 750 |
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. For example, 15% of 80 = 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. For example, 30 out of 120 is 30 ÷ 120 × 100 = 25%.
How do I add a percentage to a price?
Multiply the price by 1 plus the rate. To add 20% to 50, calculate 50 × 1.2 = 60. To remove 20%, multiply by 0.8: 50 × 0.8 = 40.
How do I remove a percentage that was already added?
Divide instead of subtracting. If 60 already includes a 20% increase, the original value is 60 ÷ 1.2 = 50, not 60 − 20% = 48.