Reverse percentage calculator
Reverse Percentage Calculator
Use this reverse percentage calculator to recover the original value before a percentage increase or decrease was applied. It shows the original value and the size of the change in money or units.
Original value
100
If 80 is after a 20% decrease, the original value was 100 and the change amount was 20.
Change amount
20
Final amount
80
How it works
Work backward from the final number
A reverse percentage calculator starts from the final amount and the known percentage change. It divides by the right multiplier to recover the number that existed before the increase or decrease happened.
Formula
original = final ÷ (1 ± percentage)
Use 1 - percentage when the final number came after a decrease, and 1 + percentage when it came after an increase.
Worked example
- 1. Start with a final amount of 80.
- 2. The 20% change is a decrease, so the remaining multiplier is 0.8.
- 3. Divide 80 by 0.8.
- 4. The original value was 100.
When people use this
- Discounts: recover the original price before the sale.
- Tax: estimate the pre-tax amount when you know the final total.
- Growth: work back to the starting value before an increase.
- Reports: reverse a known percentage movement to recover the baseline figure.
Related calculators
Keep moving through the percentage cluster
Reverse percentage fits naturally beside discount and tax pages because those tools often give you a final number first. It also pairs with the increase and decrease calculators when you want to move backward instead of forward.
Price reduction
Discount Calculator
Use the discount page when you want the final sale price after a percentage cut.
Tax use case
Tax & VAT Calculator
Use the tax page when you want to add a percentage rate on top of a base amount.
Downward change
Percentage Decrease Calculator
Use the decrease page when you know the original value and want to move forward instead of backward.
Salary use case
Salary Increase Calculator
Move forward from a current salary and raise percentage to the new salary.