Percentage change is used to measure growth, decline, price movement and performance over time. The calculation is simple, but choosing the wrong starting value can produce a misleading answer.
Use the free Percentage Calculator while following the examples below.
The percentage change formula
Subtract the original value from the new value. Divide the difference by the absolute value of the original number, then multiply by 100.
If a price rises from 80 to 100, the difference is 20. Divide 20 by 80 and multiply by 100 to get a 25% increase.
Percentage increase versus percentage decrease
A positive result represents an increase and a negative result represents a decrease. Report the direction as well as the size of the change.
A fall from 100 to 75 is a 25% decrease. Returning from 75 to 100 is a 33.33% increase because the starting values are different.
Common calculation mistakes
Do not divide by the new value. The original value is the comparison baseline. A starting value of zero also makes the standard percentage-change formula undefined.
For zero baselines, report the absolute change or explain that a percentage comparison is not meaningful.
Practical checklist
- Work from an accurate original value or source file.
- Review the selected settings before processing.
- Check the result instead of assuming it is correct.
- Keep the original until the new result has been verified.
Frequently asked questions
Is percentage change the same as percentage difference?
No. Percentage change compares an old value with a new value. Percentage difference compares two values without treating either one as the starting point.
Can percentage change exceed 100%?
Yes. Moving from 50 to 125 is a 150% increase.
What if the original value is negative?
State the calculation method clearly because percentage changes involving negative values can be difficult to interpret.
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Last reviewed: November 11, 2026.