RightFigures

Math

Percentage calculator

Find a percent of a number, what percent one number is of another, or the whole when you know the part and the percent.

Free to useNo sign-upCalculated in your browser

Your numbers

All required fields use digits only. Choose one question.

Which question
Percent

0–10,000%. Up to 6 decimal places.

0–100,000,000. Up to 6 decimal places.

0–100,000,000. Up to 6 decimal places.

Your numbers stay in this browser.

Your result

Choose a question and enter the two numbers it needs. Changing an input clears the previous result.

Ordinary percent arithmetic · Half-up at 6 decimals · Not tax or interest

Three percentage questions

A percent is a number of hundredths. This calculator answers one of three questions at a time:

  1. What is this percent of a number? Multiply the number by the percent and divide by 100.
  2. What percent is one number of another? Divide the first number by the second and multiply by 100.
  3. This amount is this percent of what? Divide the amount by the percent and multiply by 100.

Those are the same identity written three ways. The BLS note on percent changes uses the same “divide by the starting value” idea for a change; here the starting value is simply the whole.

Rounding

Every result is computed from exact fractions of a million, then rounded half up to six decimal places. Halfway cases move away from zero. Unsupported text — signs, commas, extra decimals — is rejected instead of being rewritten.

A percent of zero is not defined, and you cannot recover a whole from 0%. Both are errors.

Example

15% of 200 is 30. 30 is 15% of 200. 30 is 15% of 200. 1 is 33.333333% of 3; 2 is 66.666667% of 3.

Limits

This does not add sales tax, compound interest or convert between markups and margins. Use the percentage change calculator when you have an old value and a new value, and the discount calculator for a price markdown.

Frequently asked questions

Why can a result have six decimals?A third of a number does not land on two decimals. Six places is enough to show the half-up decision without pretending the value is a dollar amount.

Can the percent be over 100? Yes. 150% of 80 is 120. Percents above 10,000% are rejected so a missed decimal does not become an enormous silent result.

Are my numbers sent anywhere? No. The calculation stays in this browser. Analytics may record that this calculator ran, never the numbers you typed.

Sources & review

Last reviewed: . The formula is reproduced above so you can check the math independently.

Ordinary arithmetic for the numbers you enter. This is not a tax, markup, interest or compounding calculator.