Percentage Calculator

Percent means per hundred. If a number is the whole, a percent is that many hundredths of it. Twenty percent of 150 is 30 because 20 hundredths of 150 is 30. This calculator does that arithmetic in the browser, along with what percent one number is of another, a change between two numbers, a discount, and a reverse that finds the price before a percent off.

What percent asks how large one number is compared with another. Thirty is 20 percent of 150. The second number is the base, and it cannot be zero, because there is nothing to divide by. Percent change compares an old number with a new one. From 80 to 100 is an increase of 25 percent, and the difference is 20. The starting number cannot be zero. A decrease uses the same tab when the new number is smaller.

The discount mode is the shopping version, and it lives on this page only. Enter a price and a percent off between 0 and 100. A 25 percent discount on 80 saves 20 and leaves 60. A negative price is rejected, and so is a discount above 100 percent. Amounts are rounded to the nearest cent. Reverse does the opposite: if you paid 80 after 20 percent off, the original price is 100. A full 100 percent off cannot be reversed.

Nothing you type is stored or sent anywhere. Empty boxes and values such as 1e2 are rejected so the page does not guess. Very large numbers are refused. Use the tip calculator when you are splitting a bill. Income tax and a profit margin are different questions, so use the finance tools linked beside this page for those. This page does not compute them.