How is percentage change calculated?

Subtract the old value from the new one, divide by the old value, and multiply by 100. From 100 to 150 is (150 − 100) ÷ 100 × 100 = +50%, an increase. From 200 to 100 is −50%, a decrease.

Why does going up 50% and then down 50% not get me back?

Each percentage is measured against a different starting value. 100 up 50% is 150; 150 down 50% is 75.

What happens when the starting value is negative?

The change is measured against the size of the starting value, so −100 to −50 is a rise of 50%. The calculator says so when it applies.

What if the old value is 0?

A change from 0 can't be written as a percentage, because it divides by 0. The calculator says so rather than showing 0%.

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Percentage Calculator

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+50%increase

(150 − 100) ÷ 100 × 100 = +50%

Absolute change: +50

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Frequently asked questions

How is percentage change calculated?: Subtract the old value from the new one, divide by the old value, and multiply by 100. From 100 to 150 is (150 − 100) ÷ 100 × 100 = +50%, an increase. From 200 to 100 is −50%, a decrease.
Why does going up 50% and then down 50% not get me back?: Each percentage is measured against a different starting value. 100 up 50% is 150; 150 down 50% is 75.
What happens when the starting value is negative?: The change is measured against the size of the starting value, so −100 to −50 is a rise of 50%. The calculator says so when it applies.
What if the old value is 0?: A change from 0 can't be written as a percentage, because it divides by 0. The calculator says so rather than showing 0%.

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