Guide1 min readUpdated July 1, 2026

How to calculate a percentage

Short answer

To find X% of a number, multiply the number by X/100. To find what percent A is of B, divide A by B and multiply by 100. A percentage is just a fraction out of 100.

What a percentage is

A percentage is a fraction expressed out of 100. 25% means 25 per 100, or 0.25 as a decimal. Every percentage question is one of three shapes: a percentage of a number, one number as a percent of another, or a percentage change.

Percentage of a number

Multiply the number by the percentage over 100. For 20% of 150: 150 x 20 / 100 = 30.

What percent A is of B

Divide A by B and multiply by 100. For 30 out of 150: 30 / 150 x 100 = 20%.

Percentage increase or decrease

Take the difference, divide by the original, and multiply by 100. From 80 to 100: (100 - 80) / 80 x 100 = 25% increase. See how to calculate percentage change for more.

X% of N        =  N * X / 100
A is ?% of B   =  A / B * 100
change A -> B  =  (B - A) / A * 100

The three formulas

Try it: Percentage CalculatorCalculate any of the three percentage forms and copy the result.Open tool

Percentage points vs percentGoing from 10% to 15% is a 5 percentage-point rise, but a 50% increase in relative terms. Keep the two apart when reporting changes.

References

Percentage on Wikipedia — Wikipedia

Questions

How do I find what percentage one number is of another?

Divide the part by the whole and multiply by 100. For example, 45 out of 60 is 45 / 60 x 100 = 75%.

How do I add a percentage to a number?

Multiply the number by (1 + percentage/100). To add 15% to 200: 200 x 1.15 = 230.

Does this calculator send my numbers anywhere?

No. Percentage calculations run entirely in your browser tab. Nothing you type is uploaded or stored.