Percentage Calculator
Find a percent of a number, or what percent one number is of another.
Pick a question and fill both fields — the answer appears as you type.
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How to use it
- 1
Choose the sentence that matches your question.
- 2
Fill in the two numbers you already know. The third appears as you type.
- 3
Read the formula underneath if you want to check the steps, or open a scene page for a change, a difference, a discount, a tip, a test score, or a fraction.
What this calculator does
A percentage is a number out of one hundred. “15% of 80” means 15 parts in every 100 parts of 80, which is 12. The three boxes on this page are the same relationship written three ways: a percent of a whole, a part as a percent of a whole, and the whole when you already know the part and the percent.
This page does not measure how much a value rose or fell, and it does not measure how far two values sit from their average. Those are different formulas. Use the increase, decrease, or difference pages for those questions. Calculations stay in your browser; the numbers you type are not sent to our servers.
Results use decimal arithmetic, not binary floating point, so ordinary money amounts should not pick up a tail of junk digits. The default display rounds to two decimal places, half-up and away from zero (2.005 becomes 2.01, and −2.005 becomes −2.01). You can switch to more digits when you need to see more of a repeating value such as 1/3.
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Frequently asked questions
Do my numbers leave this device?
No. The arithmetic runs in your browser. Nothing you type is uploaded to our servers.
How is “15% of 80” calculated?
Multiply 80 by 15, then divide by 100. The result is 12. The same method works for any other pair of numbers you enter in the first sentence.
What if I only know the part and the percent?
Use the third sentence. If 12 is 15% of some whole, divide 12 by 15 and multiply by 100. The whole is 80. A percent of 0 has no corresponding whole — the page will say so instead of showing Infinity.
Is a percentage change the same as a percentage difference?
No. A change takes one value as the starting point. From 100 to 200 is an increase of 100%, and from 200 to 100 is a decrease of 50%. A difference compares both values to their average, so 100 and 200 differ by 66.67%. The increase, decrease, and difference pages keep those formulas apart and show the other result for the same numbers.
How are results rounded?
The default is two decimal places, rounding half-up away from zero. Use the more-digits option to see at least six places. A value such as 10% of 19.99 is exactly 1.999 and displays as 2.00 at two places.