Everyday Math Utility
Percentage Calculator
Solve three common percentage questions with the formula shown directly beside the calculation.
What is X% of Y?
Use this when you know the percentage and the base value.
X is what percent of Y?
Use this to express one positive value as a percentage of another.
Percentage change
Compare a positive starting value with a new value.
The three formulas
Percent of a number: result = (X ÷ 100) × Y.
One value as a percent of another: percentage = (X ÷ Y) × 100.
Percentage change: change = ((new − old) ÷ old) × 100.
Worked examples
- 15% of 200 = 0.15 × 200 = 30.
- 30 is what percent of 120? 30 ÷ 120 × 100 = 25%.
- From 50 to 65: (65 − 50) ÷ 50 × 100 = 30% increase.
Why percentage change can be asymmetric
A rise and an equal-size percentage fall do not generally cancel because the second percentage is applied to a different base. For example, increasing 50 by 100% produces 100, while decreasing 100 by 50% returns to 50.
Boundary cases and limitations
Division by zero is undefined. The second and third calculators therefore require a positive non-zero comparison or starting value. If your use case requires a negative baseline, calculate the ratio deliberately and interpret the sign in context rather than relying on this simplified everyday calculator.
A percentage describes a mathematical relationship. It does not, by itself, establish whether a change is important, good, bad, statistically meaningful, or financially advisable.
Privacy
All arithmetic runs in the browser. The values entered into these forms are not needed by a server to produce the result.
Common questions
Can a percentage be above 100%?
Yes. If the part is larger than the comparison whole, the ratio can exceed 100%.
What is the difference between “percent of” and “percent change”?
“Percent of” compares a part with a reference amount. Percentage change compares a new value with an earlier starting value.
Why does percentage change use the starting value?
The starting value is the reference baseline. Changing the baseline changes the percentage.
For organizations
If you operate a website, learning resource, agency project, or developer platform and want to evaluate this utility as a maintained embed, see publisher use cases and agency use cases. PTH Embed is currently a controlled beta with selective qualified tools and aggregate usage metering.