🧮 Math
Percentage Calculator
Three modes: calculate percentages, find what percent one number is of another, or measure percentage change.
What is X percent of Y?
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Percentage formulas used
- X% of Y = (X / 100) × Y
- X is what % of Y = (X / Y) × 100
- % change from X to Y = ((Y − X) / |X|) × 100
Common percentage examples
- 15% of 200 = 30
- 30 is 15% of 200
- Going from 80 to 100 = +25% change
- Going from 100 to 80 = −20% change
Why percentage change is not symmetric
A 20% decrease followed by a 20% increase does not return you to the original number. Starting at 100: −20% = 80, then +20% of 80 = 96, not 100. This is why percentage change always specifies direction.