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Reverse Percentage Calculator
Find the original amount before a percentage increase or decrease by dividing the final value by the right factor.
Reverse percentage calculator
Original amount: —
Amount of the change: —
Check: original times the factor: —
—
How to use the Reverse Percentage Calculator
- Enter the final value you have after the change.
- Enter the percentage that was applied and choose increase or decrease.
- Read the original amount and the size of the change.
Features
- Reverses percentage increases and decreases
- Shows the exact factor that was divided by
- Includes a check line that rebuilds the final value
- Flags factors of zero instead of failing
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Frequently Asked Questions
Common questions about the free online reverse percentage calculator.
Divide the final value by one minus the discount rate as a decimal. A price of 120 after 20
percent off started at 150.
For an increase divide by one plus the rate; for a decrease divide by one minus the rate,
with the rate written as a decimal.
The percentage was taken from the original amount, not the final one, so subtracting it from
the final value gives the wrong answer.
Divide the final amount by one plus the rate. If 100 grew by 25 percent to 125, then 125
divided by 1.25 returns 100.
The formula divides by zero, so the original amount is undefined. The tool reports this
instead of returning a false number.
Reverse the most recent change first, then the one before it, working backwards through each
step in turn.
No. The original amount is worked out locally in your browser, so nothing you type is sent to
a server.
Yes. It is free, unlimited and needs no account or installation on any modern device.
Last updated: October 10, 2026