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Percentage Calculator

Three percentage calculators on one page: X% of a number, what percent one number is of another, and the whole from a part. Each one shows its formula with your numbers.

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What is X% of Y?

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X is what percent of Y?

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X is P% of what?

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How to use the Percentage Calculator

  1. Find the row that matches your question: What is X% of Y?, X is what percent of Y?, or X is P% of what?
  2. Type your numbers into the boxes in that row. Decimals and negative numbers are fine.
  3. Press Calculate on the row. The answer appears next to it, with the formula filled in with your numbers.

How it works

Each row uses one formula:

  1. What is X% of Y? X ÷ 100 × Y
  2. X is what percent of Y? X ÷ Y × 100
  3. X is P% of what? X ÷ (P ÷ 100)
  • X: the part, or the percentage in row 1
  • Y: the whole
  • P: a percentage

Examples

  • 15% of 80 = 12.
  • 45 is 75% of 60.
  • 30 is 20% of 150.

The three rows with the page examples

Percentage Calculator with three rows: 15% of 80 equals 12, 45 is 75% of 60, and 30 is 20% of 150, each with its formula
The three percentage questions with their formulas.

Each row with its example from above: 15% of 80 is 12, 45 is 75% of 60, and 30 is 20% of 150. Every row shows its formula with the numbers filled in. This example is one of the automated tests for the tool, so a code change that gives a different answer fails the test run.

Percentages in everyday life

A percentage is a number out of 100. 15% means 15 out of every 100, or 0.15 as a decimal. The three rows cover most real questions:

  • X% of Y: a 15% tip on a bill of 80, or 20% of a budget
  • X is what percent of Y: a score of 45 out of 60, or how much of a goal you have reached
  • X is P% of what: working back to the full price from a deposit of 30 that was 20% of it

A quick mental check

10% of a number moves the decimal point one place to the left, so 10% of 80 is 8. Half of that, 5%, is 4, which makes 15% equal to 8 + 4 = 12.

Limitations

  • Row 2 needs a Y other than 0, and row 3 needs a P other than 0. Otherwise the result is "Cannot divide by zero".
  • Results are shown with up to 6 decimal places. The calculation itself runs at full precision.
  • For the change between an old and a new value, use the percentage increase or percentage decrease calculator.
  • For a share of a length of time, such as 25% of 1 hour 30 minutes, use the Time Percentage Calculator. It takes hours, minutes, and seconds, so you don't have to convert to decimals first.

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12.

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

Divide the part by the whole and multiply by 100. For example, 45 ÷ 60 × 100 = 75%.

How do I find the original number from a percentage?

Divide the part by the percentage expressed as a decimal. For example, if 30 is 20%, the whole is 30 ÷ 0.20 = 150.

Often used together with Percentage Calculator.