Reverse Percentage Calculator
Use this calculator when you know the final amount and the percent that was applied, and you need the original. Subtracting the same percent from the new amount does not undo an increase.
How this is calculated
The final amount is the original multiplied by a factor. Divide by that factor to recover the original.
original = final / (1 ± percent / 100)
- After an increase, divide by 1 plus the rate. 110 / 1.10 = 100.
- After a decrease, divide by 1 minus the rate. 90 / 0.90 = 100.
- A 100% decrease is not reversible, because the factor would be zero.
110 decreased by 10% is 99, not 100. That is why reverse percentage is a division, not a second application of the same percent.
Not the same as
Reverse percentage looks backward. The nearby tool looks forward.
- Increase or decrease by a percent That tool starts with the original and applies a percent. This tool starts with the final amount and removes the percent. Open increase or decrease by a percent
Related tools
Reverse-percentage questions
100. Divide 110 by 1.10.
100. Divide 90 by 0.90.
10% of 110 is 11, so 110 − 11 = 99. The 10% was taken on the original amount, not on the final amount.
Change needs both original and new values. Reverse percentage needs the final amount and the percent that was applied.
No. The factor would be zero. The calculator reports that the percentage must be less than 100 in that mode.
200. That is the same reverse-decrease math with shopping labels, also available on the discount calculator.