Percentage Calculator
Calculate a percentage of a number, one value as a percentage of another, or percentage increase and decrease with clear formulas.
Set your values
Adjust the values, then calculate your result.
How to use Percentage Calculator
- Choose the percentage question you want to answer.
- Enter A and B as labeled in that question; decimals and negative values are accepted.
- Calculate to see the result and formula.
Three common percentage questions
Percentage of a number uses A divided by 100 and multiplied by B. A as a percentage of B divides A by B and multiplies by 100. Percentage change divides the difference between B and A by the absolute value of A, then multiplies by 100; this absolute-baseline convention keeps the direction explicit when A is negative.
Check the baseline before interpreting change
A zero denominator makes a ratio undefined, and a change from zero has no finite baseline percentage. Percentage points are different from percentage change: moving from 20% to 25% is five percentage points and a 25% relative increase. Results use browser floating-point arithmetic and are rounded for display, so use a decimal accounting system when exact financial rounding is required.
What happens when the starting value is zero?
A relative percentage change from zero is undefined. The calculator reports that instead of inventing a finite percentage.
Is input uploaded?
Processing takes place in your browser. This tool does not send your input or selected files to a conversion API.