How do I calculate percentage change?

Subtract the original from the new value, divide by the original, then multiply by 100. Formula: ((new − original) / |original|) × 100.

What is the percentage increase from 80 to 100?

The percentage increase is 25%. Calculation: ((100 − 80) / 80) × 100 = 25%.

What is the percentage decrease from 200 to 150?

The percentage decrease is 25%. Calculation: ((150 − 200) / 200) × 100 = −25%.

What if the starting value is zero?

A percentage change from zero is undefined, because the formula divides by the original value. The calculator shows "Cannot divide by zero" instead of a percentage and still shows the absolute change.

Why does swapping the two numbers give a different answer?

Percentage change is measured against the starting value. Going from 80 to 100 is a 25% increase, but going from 100 to 80 is a 20% decrease, because the base changes.

Percentage change calculator

Enter a starting value and an ending value to calculate the percentage change. A positive result means an increase; negative means a decrease. The formula and absolute change are shown.

From (original value)To (new value)

Enter both numbers to see the result

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How it works

The tool subtracts the original value from the new one, divides by the absolute value of the original and multiplies by 100: ((100 − 80) / |80|) × 100 = 25%. Dividing by the absolute value keeps the sign meaningful for negative starting values, so a move from −50 to −25 reads as a 50% increase. The absolute change (+20 here) is shown under the result.

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Related operations

For working out fractions of a value, try the fraction calculator. To split a bill including a tip, use the tip calculator. For modelling savings growth over time, see the compound interest calculator.

Frequently asked questions

How do I calculate percentage change?: Subtract the original from the new value, divide by the original, then multiply by 100. Formula: ((new − original) / |original|) × 100.
What is the percentage increase from 80 to 100?: The percentage increase is 25%. Calculation: ((100 − 80) / 80) × 100 = 25%.
What is the percentage decrease from 200 to 150?: The percentage decrease is 25%. Calculation: ((150 − 200) / 200) × 100 = −25%.
What if the starting value is zero?: A percentage change from zero is undefined, because the formula divides by the original value. The calculator shows "Cannot divide by zero" instead of a percentage and still shows the absolute change.
Why does swapping the two numbers give a different answer?: Percentage change is measured against the starting value. Going from 80 to 100 is a 25% increase, but going from 100 to 80 is a 20% decrease, because the base changes.

Last reviewed September 30, 2026

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