Percentage calculator

Five common percentage questions in one place. Type the numbers and the answers update as you type, with the formula behind each one.

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  • Runs in your browser
percentage-calculator
What is X% of Y?
X is what percent of Y?
Percentage change from A to B
Increase or decrease an amount by a percentage
X is P% of what number?

Fill in the values above to see the result.

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How it works

Find your question

Percent of a number, what percent, change between two values, increase or decrease, or the whole.

Type the numbers

The answers appear straight away, and each one shows its formula.

Copy what you need

Use the copy button next to a result.

The five percentage questions everyone asks

Percentages turn up in shopping, work, school and money. A discount, a tip, an exam mark, a rise in prices or a tax rate all come down to the same few calculations, and they are easy to get backwards. This page puts the five most common ones side by side, each with its own inputs, so you can find the one that matches your question and see the formula behind the answer.

What each calculator answers

  • What is X% of Y? Multiply Y by X and divide by 100. It gives 15% of 200 as 30, the size of a tip, a deposit or a commission.
  • X is what percent of Y? Divide X by Y and multiply by 100. It turns "30 out of 120" into 25%, useful for marks, completion rates and shares.
  • Percentage change from A to B. Take the difference, divide it by the starting value and multiply by 100. Going from 80 to 100 is a 25% increase; going back from 100 to 80 is a 20% decrease, not 25%, because the starting point is different.
  • Increase or decrease by a percentage. Multiply by one plus (or minus) the percentage. A price of 200 raised by 15% is 230; lowered by 15% it is 170.
  • X is P% of what number? Divide X by the percentage as a fraction. If 30 is 25% of a number, that number is 120. It is the way to find an original price from a discounted one.

Why an increase and a decrease do not cancel out

A 20% rise followed by a 20% fall does not bring you back to the start: 100 becomes 120 and then 96. The second percentage is applied to a different base. The same is true of a price that is increased by 10% and later reduced by 10%. When you compare two values, always decide which one is the starting point, since that is the number you divide by.

Percentage points versus percent

When a rate moves from 4% to 6%, it has risen by two percentage points, but the rate itself has grown by 50% (2 divided by 4). Both statements are right and mean different things; the change calculator gives the second. If you need the first, subtract the two rates.

What it does not do

The calculator works with plain numbers and does not know about currencies, rounding rules or taxes. For prices with tax use the VAT calculator, and for shop discounts the discount calculator. Results are shown with up to four decimals.

More calculators

Frequently asked questions

How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For 15% of 200 the result is 200 × 15 ÷ 100 = 30.
How do I work out what percent one number is of another?
Divide the first by the second and multiply by 100. 30 out of 120 is 30 ÷ 120 × 100 = 25%.
How do I calculate percentage change?
Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 100 the change is +25%.
Why is a 20% increase followed by a 20% decrease not the same as before?
Because the decrease is taken from a bigger number. 100 rises to 120, and 20% of 120 is 24, so it falls to 96.
How do I find the original price before a discount?
Use "X is P% of what number?" with the sale price and the percentage you pay (100 minus the discount).
Is my data sent anywhere?
No. The calculations are done in your browser.

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