toolsxuloPercentage Calculator - 9/14/2026
Percentage Calculator
Calculate percentages, percentage change, and percentage of a total.
Calculation
%
Quick percent
Result
30
(20 ÷ 100) × 150 = 30
How it works
"Percent" just means "per hundred" - 25% of a number is the same as multiplying it by 25/100 (0.25). This tool covers the six percentage questions people actually run into in practice: what is X% of Y, what percent is X of Y, by what percent did a value change, increasing or decreasing a value by X%, and finding the original number when you only know a percentage of it.
Read the full guideHow to use it
- Pick which of the six calculations you need.
- Enter the two numbers involved - field labels update to match what each one means for that calculation.
- The result, and the formula used to get it, update instantly as you type.
Examples
20% of 15030
30 is what % of 15020%
Change from 80 to 100+25%
Increase 200 by 15%230
150 is 30% of what?500
Frequently asked
- How is percentage change calculated?
- (new value - old value) / old value × 100. A drop from 100 to 80 is -20%, and a rise from 80 to 100 is +25% - notice those aren't symmetric, which trips people up.
- What if the starting number is 0?
- Percentage change from 0 is undefined (you can't divide by zero) - the tool shows an inline message in that case rather than a misleading number.
- What's the difference between "increase by X%" and "X% of Y"?
- "X% of Y" just returns the portion (e.g. 20% of 150 is 30). "Increase X by Y%" adds that portion back onto the original value (e.g. increasing 150 by 20% gives 180, i.e. 150 + 30).
- How does the reverse calculation work?
- "Y is X% of what?" answers questions like "$150 is a 30% deposit - what's the full price?" by dividing Y by (X ÷ 100), effectively undoing a percent-of calculation.