Percentage Change Calculator
Every everyday percentage question in one place. Work out the percentage increase or decrease between two values, find a percentage of a number, see what percent one number is of another, or add or subtract a percentage.
Calculate a percentage
Percentage formulas
| Question | Formula |
|---|---|
| Percentage change | (new − old) ÷ |old| × 100 |
| A% of B | A ÷ 100 × B |
| A is what % of B | A ÷ B × 100 |
| Increase B by A% | B × (1 + A ÷ 100) |
| Decrease B by A% | B × (1 − A ÷ 100) |
| Percentage difference | |A − B| ÷ ((A + B) ÷ 2) × 100 |
Worked examples
A price rises from 80 to 100
- (100 − 80) ÷ 80 × 100 = +25%
A price falls from 100 to 80
- (80 − 100) ÷ 100 × 100 = −20%
15% of 240
- 0.15 × 240 = 36
Common percentage traps
- Ups and downs aren’t symmetrical: a 50% drop needs a 100% rise to get back to the start.
- Percent vs percentage points: an interest rate going from 4% to 5% is a rise of 1 percentage point, but a 25% increase.
- Change vs difference: percentage change has a direction (old → new); percentage difference compares two values with no “before” and “after”.
Frequently asked questions
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100.
How do I find 20% of a number?
Multiply the number by 0.2. 20% of 350 is 70.
How do I reverse a percentage increase?
Divide by 1 plus the percentage. If a price after a 25% rise is 100, the original was 100 ÷ 1.25 = 80.