To undo an increase, divide the final value by the growth factor. Subtracting the same percentage from the final value gives the wrong answer because the base has changed.
Build the growth factor
Add the increase to 100%. A 25% increase means the final value is 125% of the original, or 1.25 times the original.
Divide the final value
If a price is $100 after a 25% increase, calculate $100 ÷ 1.25. The original price was $80.
Why subtracting 25% fails
Twenty-five percent of the final $100 is $25, leaving $75. But the original increase was 25% of $80, which is $20. The percentage uses a different base.
Reverse several changes
For multiple increases, multiply their growth factors first. An increase of 10% followed by 20% gives 1.10 × 1.20 = 1.32; divide the final value by 1.32.
A calculator is often the quickest way to check your mental math. The important part is using the right starting value.
Open a calculator →Common questions
A value is 30% higher and now equals 260. What was it?
260 ÷ 1.30 = 200.
Is reversing an increase the same as a decrease?
No. The percentages use different base values.
How do I reverse a 5% increase?
Divide the final value by 1.05.
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