Free online tool
Percentage Calculator
Calculate a percentage of a number, compare two values, or measure a percentage change.
Percentages appear in schoolwork, discounts, statistics, recipes, sports, and everyday decisions. Choose the question that matches what you need to find.
How to use it
- Select the type of percentage question.
- Enter values A and B.
- Read the result and the formula shown underneath it.
Good to know
Percent means “per hundred,” so 25% is the same as 25/100 or 0.25.
For percentage change, the original value is used as the denominator.
Behind the answer
How this calculator works
For “A% of B,” the formula is (A ÷ 100) × B. For “A is what percent of B,” the formula is (A ÷ B) × 100. Percentage change uses ((new value − original value) ÷ original value) × 100.
The denominator matters. A rise from 50 to 75 is a 50% increase because the 25-point change is compared with the original 50. Reversing the comparison produces a different percentage.
Worked example
Twenty percent of 80 is 16: 20 ÷ 100 × 80 = 16. If a price changes from $80 to $100, the increase is 25%: ($100 − $80) ÷ $80 × 100 = 25%.
Assumptions and limitations
- A percentage change from an original value of zero is undefined.
- Displayed rounding can hide small differences in the underlying decimal result.
- Percentage points and percent change are different: moving from 20% to 25% is 5 percentage points but a 25% relative increase.
Common questions
Can a percentage be greater than 100%?
Yes. A value can be more than the comparison value, and an increase can exceed the original amount.
Can percentage change be negative?
Yes. A negative result indicates that the new value is lower than the original value.