Percentage Calculator
Calculate a percentage of a value, what percent one value is of another, percentage change, and original values.
All calculations run in your browser. Inputs are not sent to a server.
Percentage calculators
What percentage is X of Y?
Find the share of one value in another.
Formula: (X / Y) × 100
What is P% of X?
Calculate a percentage of a value.
Formula: (P / 100) × X
Percentage change
Compare an initial value with a final value.
Formula: ((Final − Initial) / Initial) × 100. A negative result means a decrease.
Find the original value
Recover the whole when a percentage and its result are known.
Formula: Original = H / (P / 100)
How the percentage formulas work
Percent means “per hundred”. A percentage is therefore a fraction with an implicit denominator of 100. Keeping the numeric value and the displayed formatting separate avoids rounding errors when one result is reused in another calculation.
| Question | Formula |
|---|---|
| What percent is X of Y? | (X / Y) × 100 |
| What is P% of X? | (P / 100) × X |
| Percentage change | ((Final − Initial) / Initial) × 100 |
| Original value | H / (P / 100) |
Percentage change versus absolute change
An absolute change of 25 means the value moved by 25 units. A percentage change of 25% means the value moved by one quarter of the starting value. These are different measurements and should not be used interchangeably when comparing prices, budgets, or measurements.
Frequently asked questions
Why is a zero denominator rejected?
Division by zero has no finite percentage result. The calculator explains the error instead of displaying infinity.
Can percentages be negative?
Yes. A negative percentage change describes a decrease. A negative input percentage is also mathematically valid, although its real-world meaning depends on the context.
How many decimal places are shown?
Results are rounded for display to at most six decimal places. Calculations use the unrounded internal value.