Percentage Calculator

Work out X% of a number, what percentage one number is of another, percentage increase or decrease, and a discounted price.

Reviewed by Dany, RightSums team · Updated

Runs in your browser. Free, no sign-up.

personal-finance · Daily life · UK & US

Pick one of four modes and type two numbers. The answer updates as you type, with a line underneath showing the formula used. 'What is X% of Y' multiplies Y by X divided by 100. 'X is what % of Y' divides X by Y and multiplies by 100. '% Increase / Decrease' takes the difference between the new and original values, divides it by the original and shows the result with a plus or minus sign, along with the raw difference. 'Discount Price' takes a percentage off an original price and tells you how much you save and what you pay. It suits sale prices, pay rises, exam marks, price changes and working out shares of a total.

Accepted inputs

  • Calculation mode (X% of Y, X is what % of Y, % change, discount)
  • First value
  • Second value

Outputs

  • Answer
  • Formula and working in words
  • Difference (percentage change mode)
  • Saving and final price (discount mode)

How to use the Percentage Calculator

  1. Choose a mode: X% of Y, X is what % of Y, percentage increase or decrease, or discount price.
  2. Enter the first value, which is the percentage, the part, the original value or the original price depending on the mode.
  3. Enter the second value, which is the total, the new value or the discount percentage.
  4. Read the answer and the explanation beneath it, which repeats the formula with your numbers.

Frequently asked questions

How do I work out a percentage of a number?

Divide the percentage by 100 and multiply by the number. 20% of 150 is (20 ÷ 100) × 150 = 30. In the calculator, choose 'What is X% of Y', enter 20 and 150, and the answer and formula appear straight away.

How do I calculate percentage increase?

Subtract the original value from the new value, divide by the original and multiply by 100. A rise from 80 to 100 is (100 - 80) ÷ 80 × 100 = 25%, shown as +25%. A fall from 100 to 80 is a 20% decrease, because you divide by the starting value of 100.

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

Divide the part by the whole and multiply by 100. If you scored 45 out of 60, that is (45 ÷ 60) × 100 = 75%. Use the 'X is what % of Y' mode and enter the part first and the total second.

How do I calculate a discount?

Multiply the price by the discount percentage, divide by 100 and take the result off the price. 15% off £60 saves £9, so you pay £51. The Discount Price mode shows both the saving and the final price.

Why does a 20% rise followed by a 20% fall not get back to the start?

Because each percentage is taken from a different starting value. £100 up 20% is £120, but 20% of £120 is £24, so a 20% fall leaves £96. Run each step through the percentage change or discount mode to see it.

Related tools

  • Tip Calculator and Bill Splitter

    Add a tip to a restaurant bill and split it evenly between any number of people. Pick 10%, 12.5%, 15%, 18% or 20% and see what each person pays.

  • Unit Price Comparison Calculator

    Compare two products by unit price to see which is better value. Enter each price and pack size in g, kg, ml, litres or items.