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Percentage increase and decrease calculator

The short answer

To find a percentage increase, subtract the old number from the new one, divide by the old number and multiply by 100. Going from 80 to 100 is 20 ÷ 80 × 100, or a 25% increase. A decrease works the same way: 100 down to 80 is 20%. Enter your numbers below.

Enter an old and a new number to see the change, or raise or lower a number by a percent. Handy for prices, costs, sales and pay.

Checked November 5, 2026. How we make these tools

Percentage increase

25%

80 to 100 is a change of 20.

150 raised by 10%: 165
The difference: 15

How it works

Percent change = (new − old) ÷ old × 100.
Raise by a percent = number × (1 + percent ÷ 100).
Lower by a percent = number × (1 − percent ÷ 100).

Worked examples
From	To	Change
80	100	Up 25%
100	80	Down 20%
250	300	Up 20%
1,200	1,500	Up 25%
45	40	Down 11.1%

Why up and down don’t match

The percent is measured from wherever you start. 80 to 100 is up 25%, but 100 back to 80 is only down 20%. That’s also why a 20% discount followed by a 20% price rise doesn’t get you back to the old price: $100 becomes $80, then $96.

In Excel or Google Sheets

With the old number in A1 and the new one in B1, use =(B1-A1)/A1 and format the cell as a percentage.

Using it in your business

Costs went up? Enter last year’s and this year’s to see by how much, then the price increase calculator shows what a raise in your own prices does to profit, and the discount calculator shows what a sale costs you.

Common questions

How do I calculate a percentage increase?

Subtract the old number from the new one, divide by the old number, and multiply by 100. From $40 to $50 is 10 ÷ 40 × 100, or 25%.

How do I calculate a percentage decrease?

Subtract the new number from the old one, divide by the old number and multiply by 100. From $50 to $40 is 10 ÷ 50 × 100, or 20%.

How do I add 10% to a number?

Multiply it by 1.10. $150 plus 10% is $165. To take 10% off, multiply by 0.90 instead.

What’s the percentage increase formula in Excel?

=(B1-A1)/A1, with the old number in A1 and the new number in B1. Format the cell as a percentage to see 25% rather than 0.25.

How do I work out a salary increase percentage?

Use the old and new pay in the same units. A raise from $50,000 to $53,000 a year is 3,000 ÷ 50,000 × 100, or 6%.

What if the old number is zero?

There’s no percent change from zero, because you can’t divide by it. Give the change in dollars or units instead.

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