Percentage Calculator
Five common percentage questions in one place — pick the one that matches what you're trying to work out.
The formulas
| X% of Y | (X ÷ 100) × Y |
| X is what % of Y | (X ÷ Y) × 100 |
| Y is X% of what number | Y ÷ (X ÷ 100) |
| % change from X to Y | ((Y − X) ÷ X) × 100 |
| X increased/decreased by P% | X × (1 ± P ÷ 100) |
Frequently asked questions
What's the difference between "percent change" and "percentage points"?
Percent change is relative to the starting value: going from 50 to 75 is a 50% increase (25 is half of 50). Percentage points are a simple subtraction: an interest rate going from 5% to 7% rose by 2 percentage points, not "2 percent" — it's actually a 40% relative increase. Mixing these up is one of the most common percentage mistakes.
Why is the percent change undefined when I start from 0?
Percent change divides by the starting value, and dividing by zero is undefined. Going from 0 to any positive number is technically an infinite percent increase, so this tool shows that case as undefined rather than a misleading number.
Does increasing by X% and then decreasing by X% get back to the original?
No — a common trap. $100 increased by 50% is $150; $150 decreased by 50% is $75, not $100. Percentage changes are relative to whatever the current value is at the time, not the original.
How is a percentage different from a fraction or decimal?
They're three ways of writing the same thing: 20% = 20/100 = 0.2. "Percent" literally means "per hundred," which is why every formula here either divides by 100 or multiplies by it.