Math
Percentage Calculator
Find a percent of a number, reverse percentages, and percent change.
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What is P% of X?
Result
X is what % of Y?
Result
%
This free Percentage Calculator covers Find a percent of a number, reverse percentages, and percent change.
Enter the Percentage Calculator fields, then read the output. Math calculators on this site keep the formula visible beside the form, with no account required.
Using the Percentage Calculator
Find a percent of a number, reverse percentages, and percent change. Fill the labeled fields on the Percentage Calculator and read the result. The formula stays in How it works rather than being repeated here.
Worked example
What is 15% of 80? (15/100)×80 = 12. 12 is what percent of 80? (12/80)×100 = 15%. Percent change from 80 to 92: (92−80)/80×100 = 15% increase.
\[ 0.15\times 80=12;\quad \frac{12}{80}\times 100=15\% \]
FAQ
Why does percent change use the starting value in the denominator?
Percent change measures relative movement from A to B, so the baseline is A. Using B (or an average) answers a different question and will not match this calculator.
Can I reverse a percentage increase?
A 15% increase followed by a 15% decrease does not return to the original: 80→92, then 92×0.85=78.2. Undo increases with division by (1 + p/100), not another equal-percent decrease.
What's the difference between a percentage and percent change?
A percentage is a part of a whole (what is P% of X, or X as a percent of Y). Percent change is how far a value moved from its start: (new − old) / old × 100. This page has a box for each. The How to Calculate Percentage Change tutorial covers only the movement identity.