How to use
- Pick a calculation type at the top.
- Enter numbers in A and B — the result updates instantly. Thousands separators (1,000) are fine.
- Use the Copy button on the result to grab the value.
Formulas
| Calculation | Formula | Example |
|---|---|---|
| What is B% of A? | A × B ÷ 100 | 15% of 200 = 30 |
| A is what % of B? | A ÷ B × 100 | 30 is 15% of 200 |
| Increase A by B% | A × (1 + B ÷ 100) | 10,000 increased by 10% = 11,000 |
| Decrease A by B% | A × (1 − B ÷ 100) | 10,000 decreased by 10% = 9,000 |
Common pitfalls
- A 10% increase followed by a 10% decrease does not return the original value. 10,000 → 11,000 → 9,900, because the second 10% is taken from 11,000.
- Percent and percentage points differ. A rate moving from 3% to 4% rose by 1 percentage point, but by 33.3% in relative terms. Use the percent change calculator for relative change.
- For everyday cases, the discount calculator and VAT calculator are quicker.
FAQ
How many decimal places are shown?
Up to six. Floating-point noise such as 0.1 + 0.2 = 0.30000000000000004 is cleaned up automatically.
Can I enter negative numbers?
Yes. A negative percentage in “Change A by B%” simply reverses the direction.