Find a percentage increase
Subtract the original value from the new value. Divide by the original and multiply by 100. An increase from 80 to 100 is 20 ÷ 80 × 100 = 25%. The original value is the reference, so the order matters.
Percent Change Calculator
Compare an old amount with a new one to find the increase or decrease, including the actual difference.
Percent Change Calculator
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How to use this calculator
Find a percentage decrease
A change from 100 to 80 is (80 − 100) ÷ 100 × 100 = −20%. The negative sign means a decrease. The tool also shows the difference in the original units.
Why reversing the numbers changes the answer
Going from 80 to 100 is a 25% increase; returning from 100 to 80 is a 20% decrease. Each direction uses a different starting value. Equal dollar changes do not necessarily represent equal percentages.
Zero and percentage points
A starting value of zero makes ordinary percent change undefined. Also distinguish percentage points from percent change: a rate rising from 4% to 5% rises 1 percentage point, or 25% relative to its previous rate. Entering 4 and 5 calculates that relative change.
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Common questions
What if both values are equal?
The difference and percent change are zero, provided the original value is greater than zero.
Does this calculate investment returns?
It calculates simple change between two amounts. It does not include deposits, withdrawals, fees, compounding, or elapsed time.
About this tool
Created by Marchelle Cook at Roof & Ratio. These calculations run in your browser; entered values are not uploaded or saved by the calculator. Report a calculation issue with an example so we can review it.
Guide updated October 23, 2026. Displayed decimal results may be rounded; exact fraction and integer results are identified in the answer.