How to use
- Find the question that matches yours.
- Type the numbers into its boxes. The answer appears immediately on the right.
- Use negative percentages for decreases, for example -20 for a 20% discount.
Options explained
- Percentage change
- (new − old) ÷ |old| × 100. Going from 80 to 100 is +25%; going back from 100 to 80 is −20%.
- Reverse percentage
- Finds the value before a change. A price of 180 after a 10% discount was 200 before, not 198.
Examples
| Question | Answer |
|---|---|
| 15% of 80 | 12 |
| 12 is what % of 80 | 15% |
| 80 → 100 | +25% |
| 200 − 10% | 180 |
Frequently asked questions
Why is a 10% increase followed by a 10% decrease not zero?
The decrease is taken from the larger number. 100 + 10% = 110, and 110 − 10% = 99.
What is the difference between percent and percentage points?
Going from 5% to 6% is a rise of 1 percentage point, but a 20% increase in relative terms.
Can I use decimals?
Yes. Both a dot and a comma are accepted as the decimal separator.
Privacy
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