Work out a percentage of a number, what percent one number is of another, or the percentage change between two values. The working is shown with every answer, so you can check it or copy it into a report.

How to use the percentage calculator

Choose the question you want to answer from the Calculation list.
Enter the two numbers. The labels change to match the question.
The answer and the working update as you type. Use Copy result to paste them elsewhere, or Copy link to share the same calculation.

The three percentage questions

What is X% of Y?

Use this for discounts, tips, commission and anything else described as “a percentage of” an amount. Percent means “per hundred”, so 15% is 15 hundredths of the amount: divide by 100, then multiply.

X is what percent of Y?

Use this for shares and scores: 18 correct answers out of 24, or 36 sales from 240 visitors. Divide the part by the whole and multiply by 100.

Percentage change from X to Y

Use this for price rises, growth and falls. The change is always measured against the starting value (X). A positive result is an increase and a negative one is a decrease.

Formula

X% of Y = X ÷ 100 × Y
X as a % of Y = X ÷ Y × 100
% change from X to Y = (Y − X) ÷ |X| × 100

X and Y are the two numbers you enter. |X| means the size of X without its sign, so a change from a negative starting value still reads the right way round.

Worked examples

Discount: 30% off a price of 85 is 30 ÷ 100 × 85 = 25.5 off, so you pay 85 − 25.5 = 59.5.

Share: 18 out of 240 is 18 ÷ 240 × 100 = 7.5%. Check it the other way: 7.5% of 240 = 18.

Change: a price rising from 80 to 100 is (100 − 80) ÷ 80 × 100 = a 25% increase. Falling back from 100 to 80 is (80 − 100) ÷ 100 × 100 = −20%, a 20% decrease.

Common percentage mistakes

Adding and taking away percentages as if they share a base. A 10% rise followed by a 10% fall does not return to the start: 100 rises to 110, and 10% off 110 leaves 99.
Mixing up percent and percentage points. An interest rate moving from 4% to 5% has risen by 1 percentage point, which is a 25% increase in the rate.
Using the wrong base for profit. Profit as a share of the selling price (margin) and as a share of the cost (markup) are different numbers for the same sale. The profit margin calculator shows both.

Frequently asked questions

How do I add a percentage to a number?

Multiply by 1 plus the percentage divided by 100. Adding 5% to 200: 200 × 1.05 = 210.

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

Divide by 1 plus the percentage divided by 100. If 210 includes a 5% addition, the amount before it was 210 ÷ 1.05 = 200. Taking 5% off 210 gives 199.5, which is not the original.

Why is a 25% rise followed by a 20% fall back to the start?

Each percentage is taken from a different base. 80 rises 25% to 100 because the base is 80; 100 falls 20% to 80 because the base is now 100.

Can I use negative numbers?

Yes. For percentage change from a negative starting value, the calculator divides by the size of the start (|X|), so moving from −50 to −25 shows as a 50% increase.

Why can’t the starting value be zero?

Any change from zero is an infinite percentage. Use the difference (Y − X) instead.

How many decimal places are shown?

Up to four, with trailing zeros removed. The calculation itself uses full precision.

Percentage Calculator