Math
A fast, transparent percentage calculator with instant results: a percentage of a value, and that value after an increase or decrease.
Results update as you type. No calculate button. All calculations run locally in your browser.
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Enter a percentage and a base value.
| Quantity | Value |
|---|---|
| Percentage of base | — |
| Base after increase | — |
| Base after decrease | — |
| Percentage as a decimal | — |
Percentage of base = base value × percentage ÷ 100. Value after increase = base × (1 + percentage ÷ 100). Value after decrease = base × (1 − percentage ÷ 100).
15% of 280 = 280 × 15 ÷ 100 = 42. After a 15% increase: 280 + 42 = 322. After a 15% decrease: 280 − 42 = 238. Use Reset example above to reproduce this result, then replace the values with your own.
Percentages may be negative or above 100; a decrease larger than 100% gives a negative result, which is arithmetically correct but may not be meaningful for the quantity being described. Results are rounded to 2 decimal places for display. This page computes percentages only — it does not add tax, fees, or compounding unless those are part of the percentage you enter.
Multiply the base by the percentage and divide by 100. For example, 15% of 280 is 280 × 15 ÷ 100 = 42.
The base plus the percentage amount: 280 increased by 15% is 280 + 42 = 322.
Yes. 150% of 280 is 420, and a 150% increase gives 700. The arithmetic is the same; check whether that makes sense for your situation.
A negative percentage reverses the direction: −15% of 280 is −42, so an 'increase' of −15% is really a decrease to 238.
Display is rounded to 2 decimal places. The underlying multiplication is not rounded before the increase and decrease figures are computed.
Results are estimates only and do not constitute professional advice.