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Percentage calculator

Six percentage calculators on one page, so you never have to remember formulas: type the numbers and see the result instantly together with the formula used. Accepts decimals with a dot or a comma.

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What is % of ?

b × a / 100

is what percent of ?

a / b × 100

What is the % change from to ?

(b − a) / a × 100

Increase by % (negative to discount)

b × (1 + a / 100)

is % of…

a × 100 / b

Value before a % change if it is now (e.g. price before tax)

a / (1 + b / 100)

Ctrl + Enter runCtrl + C copy result

How to use

  1. 1Find the question you want to answer (for example, “What is 20% of 150?”).
  2. 2Type your numbers into the boxes; the result updates as you type.
  3. 3For discounts use a negative percentage in “Increase… by %”.
  4. 4Copy the result with the button or check the formula under each card.

Use cases

  • Work out the final price after a sale discount.
  • Add or remove sales tax or VAT from a price.
  • Measure growth in sales, traffic or salary between two periods.
  • Calculate tips, commissions, exam scores or conversion rates.

Frequently asked questions

How do you calculate a percentage of a number?

Multiply the number by the percentage and divide by 100. For example, 20% of 150 is 150 × 20 / 100 = 30.

How do I calculate a discount?

Multiply the price by (1 − discount/100). A 15% discount on $200 leaves 200 × 0.85 = $170. In the “Increase” calculator type −15.

How do I remove tax from a price?

Divide the price including tax by (1 + tax/100). With 20% VAT, £120 is 120 / 1.20 = £100 before tax. Subtracting 20% directly gives the wrong answer.

How is percentage change calculated?

Subtract the starting value from the final value, divide by the starting value and multiply by 100. From 80 to 100 is a 25% increase; from 100 to 80, a 20% decrease.

Why doesn’t +10% then −10% bring me back?

Because the second percentage applies to a different amount: 100 + 10% = 110, and 110 − 10% = 99. Successive percentages neither add up nor cancel out.

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