Percentage calculator
Pick your question. Type two numbers. You get the answer with the math written out. The calculator handles every kind of percentage problem: a percent of a number, what percent one number is of another, and the whole when you only know a part.
15% of 200 = 200 × 0.15 = 30
Updated: October 2, 2026 · Sources and methodology
The three percentage formulas
Every everyday percentage question is one equation: part = percent ÷ 100 × whole. Only the unknown changes. In other words, there is one formula, not three.
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | Y × X ÷ 100 | 15% of 200 = 200 × 0.15 = 30 |
| X is what % of Y? | X ÷ Y × 100 | 30 is 30 ÷ 200 × 100 = 15% of 200 |
| X is Y% of what? | X ÷ (Y ÷ 100) | 30 is 15% of 30 ÷ 0.15 = 200 |
Worked example: a sale price
- A $80 jacket is 25% off. 25% of 80 is 80 × 0.25 = 20.
- The sale price is 80 − 20 = $60.
- Check it backward. 20 ÷ 80 × 100 = 25%, so 20 is 25% of 80. And 20 ÷ 0.25 = 80, so 20 is 25% of 80.
Handy fact: X% of Y always equals Y% of X. 8% of 50 is hard. 50% of 8 is easy. It's 4. Same answer.
Percent, decimal and fraction chart
| Percent | Decimal | Fraction | Shortcut |
|---|---|---|---|
| 1% | 0.01 | 1/100 | move decimal 2 places left |
| 5% | 0.05 | 1/20 | 10% × 0.5 |
| 10% | 0.1 | 1/10 | move decimal 1 place left |
| 12.5% | 0.125 | 1/8 | divide by 8 |
| 20% | 0.2 | 1/5 | divide by 5 |
| 25% | 0.25 | 1/4 | divide by 4 |
| 33.33% | 0.3333 | ≈ 1/3 | divide by 3 |
| 40% | 0.4 | 2/5 | 10% × 4 |
| 50% | 0.5 | 1/2 | divide by 2 |
| 60% | 0.6 | 3/5 | 10% × 6 |
| 66.67% | 0.6667 | ≈ 2/3 | 10% × 6.667 |
| 75% | 0.75 | 3/4 | 10% × 7.5 |
| 80% | 0.8 | 4/5 | 10% × 8 |
| 90% | 0.9 | 9/10 | 10% × 9 |
| 100% | 1 | 1/1 | the whole number |
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percent by 100 to get a decimal. Then multiply. 15% of 200 is 0.15 × 200 = 30.
How do I find what percent one number is of another?
Divide the part by the whole. Multiply by 100. 30 out of 200 is 30 ÷ 200 = 0.15, which is 15%.
How do I find the original number from a percentage?
Divide the part by the percent written as a decimal. Say 30 is 15% of a number. The number is 30 ÷ 0.15 = 200.
What is the difference between percent and percentage points?
Percentage points measure the gap between two percentages. Percent measures relative change. A rate that goes from 4% to 5% rose 1 percentage point. That same move is a 25% increase.
Why is X% of Y equal to Y% of X?
Both equal X × Y ÷ 100. Multiplication works in either order. So 4% of 75 is the same as 75% of 4, which is 3.