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Percentage Calculator

Solve every everyday percentage question in one place: X% of a number, what percent one number is of another, percentage change, and increasing or decreasing by a percentage.

  • 4 calculators in one
  • Instant results
  • Shows the formula

What is X% of Y?

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X is what percent of Y?

is what % of
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Percentage increase or decrease from X to Y

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Increase or decrease a number by a percentage

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How to use the Percentage Calculator tool

  1. Pick the right calculatorChoose the box that matches your question, such as “What is X% of Y?” or “Percentage increase from X to Y”.
  2. Type your numbersResults update instantly as you type. Decimals and negative numbers are supported.
  3. Check the formulaThe formula used for your last calculation is shown below, so you can check the working or reuse it in a spreadsheet.

Four common percentage problems

  • X% of YFind a tip, a discount amount, tax, a commission or a share of a total.
  • X is what % of YTurn exam marks, survey results or budget items into percentages.
  • Percentage changeMeasure growth or decline between two values, such as prices, salaries or visitors.
  • Add or subtract a percentageApply a raise, a markup, a discount or a price increase to a number.

What is a percentage?

“Per cent” means “per hundred”. A percentage expresses a part of something as a fraction of 100, which makes very different quantities easy to compare. 25% means 25 out of every 100, the same as the fraction ¼ or the decimal 0.25.

The four formulas

1. What is X% of Y?

Result = X ÷ 100 × Y. Example: 15% of 250 = 0.15 × 250 = 37.5. Use this for discounts (“20% off”), tips, tax and commissions.

2. X is what percent of Y?

Percent = X ÷ Y × 100. Example: 45 out of 180 = 45 ÷ 180 × 100 = 25%. Use this to turn a test score, a vote count or an expense into a percentage of the total.

3. Percentage increase or decrease

Change = (New − Old) ÷ |Old| × 100. Example: a price rising from 80 to 100 is (100 − 80) ÷ 80 × 100 = +25%. Falling from 100 to 80 is −20%. The two numbers differ because each change is measured against a different starting value.

4. Increase or decrease a number by a percentage

Result = Number × (1 ± Percent ÷ 100). Example: 1,200 increased by 10% = 1,200 × 1.10 = 1,320. Decreased by 10% it is 1,200 × 0.90 = 1,080.

Common percentage mistakes

  • A rise and a fall of the same percentage don’t cancel out. If a price goes up 50% and then down 50%, you end at 75% of where you started, not 100%.
  • Percent vs percentage points. An interest rate moving from 4% to 5% is a rise of 1 percentage point, but a 25% relative increase.
  • Reversing a discount. To find the original price before a 20% discount, divide by 0.80; don’t add 20% back on. A sale price of 80 came from 80 ÷ 0.8 = 100.
  • Change from zero. Percentage change from 0 is undefined, because you can’t divide by zero.

Quick mental math tricks

  • 10% of a number: move the decimal point one place left (10% of 340 = 34).
  • 5% is half of 10%, and 20% is double 10%.
  • X% of Y equals Y% of X: 8% of 50 is the same as 50% of 8, which is 4.

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 250 is 15 ÷ 100 × 250 = 37.5.
How do I work out percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100. From 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%.
How do I find what percent one number is of another?
Divide the part by the total and multiply by 100. 45 out of 180 is 45 ÷ 180 × 100 = 25%.
How do I remove a percentage from a price?
To take 10% off, multiply by 0.90. To find the original price before a discount, divide the sale price by (1 − discount ÷ 100).
Can I use negative numbers or decimals?
Yes. All four calculators accept decimals and negative numbers.