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Percentage Calculator

Work out X% of a number, what percentage one number is of another, percentage change and reverse percentages.

  1. Enter your numbers
  2. Results update as you type
  3. Copy the answer or share the link
Runs in your browser. Your data and files never leave your device.

About the Percentage Calculator

This percentage calculator answers the four questions people ask most: what is X% of a number, what percentage one number is of another, how much something has changed in percentage terms, and what the original number was before a percentage was taken.

Pick the calculation you need, type the two numbers and the answer appears as you type, with the working shown so you can check it or copy it into your own notes.

How does the Percentage Calculator work?

A percentage is a number out of 100, so 15% means 15 ÷ 100 = 0.15. Every percentage question is a rearrangement of the same relationship: part = percentage ÷ 100 × whole.

To find X% of Y, multiply Y by X ÷ 100. To find what percentage X is of Y, divide X by Y and multiply by 100. Percentage change compares the difference with the starting value, and a reverse percentage divides by the percentage instead of multiplying.

Percentage Calculator formula

part = (percentage ÷ 100) × whole
percentage = part ÷ whole × 100
% change = (new − old) ÷ |old| × 100

Percentage change is always measured against the starting (old) value, which is why a rise from 50 to 100 is +100% but a fall from 100 to 50 is −50%.

Example

15% of 200 = 0.15 × 200 = 30.

30 is 15% of 200, because 30 ÷ 200 × 100 = 15.

A price going from 80 to 100 is a 25% increase: (100 − 80) ÷ 80 × 100 = 25.

Guides

Frequently asked questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For 20% of 350: 0.20 × 350 = 70.

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

Divide the first number by the second and multiply by 100. 45 out of 60 is 45 ÷ 60 × 100 = 75%.

Why isn’t a 50% increase cancelled by a 50% decrease?

Because each percentage is taken from a different starting value. 100 + 50% = 150, but 150 − 50% = 75, not 100.

What’s the difference between percent and percentage points?

If an interest rate moves from 4% to 5%, it has risen by one percentage point but by 25 percent (1 is 25% of 4).

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