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Percentage Calculator

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To find a percentage of a number, divide the percentage by 100 and multiply: 15% of 240 is 0.15 × 240 = 36. To find what percent one number is of another, divide and multiply by 100: 36 ÷ 240 × 100 = 15%. The five calculators below handle every common percentage question and show the working.

Also known as: percent calculator · calculate percentage · percentage finder

Percentage of a number

What is % of

What percent is it?

is what % of

Percentage change

From to

Increase or decrease by a percentage

%

Find the original number

is % of what?

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The five percentage formulas

1. X% of Y = X ÷ 100 × Y 2. A is what % of B = A ÷ B × 100 3. % change from A to B = (B − A) ÷ A × 100 4. Y increased by X% = Y × (1 + X ÷ 100) Y decreased by X% = Y × (1 − X ÷ 100) 5. A is X% of what? = A ÷ (X ÷ 100)

Worked examples

  • Tip: 15% of a 240 bill is 0.15 × 240 = 36.
  • Test score: 42 out of 50 is 42 ÷ 50 × 100 = 84%.
  • Price rise: from 80 to 100 is (100 − 80) ÷ 80 × 100 = +25%.
  • Salary raise: 2,500 increased by 4% is 2,500 × 1.04 = 2,600.
  • Sale price: 250 decreased by 20% is 250 × 0.8 = 200.
  • Before tax: if 45 is the 30% deposit, the full price is 45 ÷ 0.3 = 150.

Common mistakes

Percentage change isn't symmetrical

A price that rises from 80 to 100 goes up 25%, but falling back from 100 to 80 is a 20% drop. The change is always divided by the starting value, and the starting value is different each way. Likewise, a 50% loss followed by a 50% gain leaves you at 75% of where you began, not back at 100%.

Percent versus percentage points

If an interest rate goes from 2% to 3%, it rose by 1 percentage point, but by 50 percent (because 1 is half of 2). News reports often mix these up. Use percentage points for the difference between two percentages.

Adding percentages

Two discounts of 20% and 10% don't make 30% off. The second applies to the already-reduced price: 0.8 × 0.9 = 0.72, which is 28% off. The Discount Calculator handles stacked discounts.

Mental maths shortcuts

  • 10%: move the decimal point one place left. 10% of 240 is 24.
  • 5%: half of 10%. 5% of 240 is 12.
  • 1%: move the decimal point two places. 1% of 240 is 2.4.
  • Swap trick: 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, 20% of 150 is 0.2 × 150 = 30.

How do I calculate 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 work out what percentage one number is of another?

Divide the part by the whole and multiply by 100. 36 out of 240 is 36 ÷ 240 × 100 = 15%.

How do I find the original number before a percentage was added?

Divide by (1 + the percentage ÷ 100). If a price with 20% tax is 120, the price before tax is 120 ÷ 1.2 = 100.

What is the difference between percent and percentage points?

Percentage points are the simple difference between two percentages (2% to 3% is 1 point). Percent change is relative (2% to 3% is a 50% increase).

Last updated October 2026 · More calculators