Calculators
Percentage Calculator
Calculate X percent of Y, reverse percentages, and percentage increase or decrease.
What is X% of Y?
X% of Y
15% of 240
36
X is what percentage of Y?
Reverse percentage
45 is this percent of 180
25%
Percentage increase / decrease
Change
Increase
25%
About this tool
Percentages describe a number as a fraction of 100. This tool covers the three calculations people need most: a percent of a value, a reverse percent, and percent change.
How to use
- Use the first card to find X% of Y.
- Use the second card when you know two numbers and want the percent relationship.
- Use the third card to measure increase or decrease from an original amount.
Formula and methodology
X% of Y = (X ÷ 100) × Y. “X is what percent of Y” = (X ÷ Y) × 100. Percentage change = ((new − original) ÷ |original|) × 100. A zero original value cannot produce a percent change.
Worked example
15% of 240 is 36. 45 is 25% of 180. Going from 80 to 100 is a 25% increase.
Frequently asked questions
Is percentage decrease just a negative increase?+
Yes. If the new value is smaller, the change is negative and labelled as a decrease.
Why can’t the starting value be zero?+
Dividing by zero is undefined. A change from 0 to any other number is not a finite percentage.
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