Percentage calculator
Percent of a number, percent of a total, and percent change.
About this calculator
Pick the question you need answered: X% of a number, what percent one number is of another, or the percent change between two numbers.
Percent change is measured against the starting value, so going from 50 to 100 is a 100% increase, while going back from 100 to 50 is a 50% decrease.
How it works
Percent means per hundred. Change is the difference divided by the starting value.
Worked example
- I want: X% of a number
- Percent: 20
- Of: 150
20% of 150: 30
The story behind it
Where the idea came from: Ancient Rome. The word comes from the Latin per centum, "by the hundred".
Working in hundredths goes back at least to ancient Rome, where the emperor Augustus taxed goods sold at auction at one part in a hundred. The % sign grew out of Italian merchants' shorthand for per cento. It's still among the most common sums people do, which is why this calculator answers the three questions that come up most.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, so please double-check anything important.
- Spotted a mistake? Tell us and we'll look into it.
After 15 years as a mathematics educator, I built CalculStore to give students, teachers, professionals and anyone working with numbers simple, reliable tools.
Meet the founder