Reverse Percentage Calculator
Enter a value after a percent change below to instantly find the original value.
Original Value
100
The Reverse Percentage Formula
Original = value after change ÷ (1 + percent change ÷ 100).
Worked example
A price is $120 after a 20% increase.
120 ÷ (1 + 0.20) = 120 ÷ 1.20
Original price: $100
Frequently Asked Questions
How do you reverse a percentage change?
Divide the value after the change by (1 + the percent change as a decimal). Use a negative percent for a decrease.
If a price is $120 after a 20% increase, what was it before?
120 ÷ 1.20 = $100.
Why can't you just subtract the percentage back off the final value?
Because the percentage was originally calculated from the smaller starting value, not the larger final one — subtracting 20% of $120 (getting $96) doesn't undo a 20% increase from $100, since 20% of $100 and 20% of $120 aren't the same amount.
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