Worked example
Going from 100 to 125 is an increase of 25%.
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Everyday money
Percentage Change Calculator
Measure an increase or decrease relative to an original value.
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Adjust the example to calculate using your own figures. Results update instantly.
Your results
Calculated locally- Amount changed
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- Percentage change
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Important assumptions
Percentage change is undefined from an original value of zero; a positive starting value is required.
How to use your results
Always compare the difference with the starting value. A 20% decrease from 100 to 80 is not cancelled out by a 20% increase from 80.
Start with the example values, then replace them with amounts for the same transaction or time period. Double-check rates and units. The results are estimates intended to help you explore possible outcomes, not financial or tax advice.
Why the original value matters
Percentage change divides by the original number, not the final one. If a monthly bill rises from $80 to $100, the $20 increase is 25% of the original $80. Reversing the direction changes the denominator and gives a 20% decrease.
Comparing growth periods
Compare periods of the same length and measure. A one-month sales jump cannot be compared directly with a year of revenue growth without converting the time scale. Consider also whether the starting value was unusually low.
Why is a 20% loss not recovered by a 20% gain?
After a fall from $100 to $80, a 20% gain adds only $16, producing $96. Returning to $100 requires a 25% gain from $80.
How to calculate percentage change
Change (%) = (new value − original value) ÷ original value × 100
Always compare the difference with the starting value. A 20% decrease from 100 to 80 is not cancelled out by a 20% increase from 80.