Calculate a percentage
Switch between percentage-of, ratio and percentage-change calculations.
Calculate the percentage you actually need
This calculator handles the most common percentage questions: what percentage one number is of another, a percentage of a value, percentage increase or decrease, and the original value before a percentage change.
Common percentage formulas
| Question | Formula |
|---|---|
| What is X% of Y? | (X ÷ 100) × Y |
| X is what percentage of Y? | (X ÷ Y) × 100 |
| Percentage change | ((New − Old) ÷ Old) × 100 |
| Increase a value by X% | Value × (1 + X ÷ 100) |
| Decrease a value by X% | Value × (1 − X ÷ 100) |
Worked examples
20% of 250 is 50. If a price rises from 80 to 92, the percentage increase is 15%. If a sale price of 80 reflects a 20% discount, the original price was 100.
Percentage points are different
A change from 20% to 25% is an increase of 5 percentage points, but a relative increase of 25%. Use percentage points when comparing two rates directly.
Frequently asked questions
Why can percentage change be negative?
A negative result means the new value is lower than the original value.
Can I calculate a reverse percentage?
Yes. Use the original-value calculation when you know the final value and the percentage increase or decrease.
What happens when the original value is zero?
Percentage change is undefined when the original value is zero because the formula requires division by zero.
For price-specific calculations, use the Discount Calculator or VAT Calculator.