Reverse Percentage Calculator
Find the original value before a percentage increase or decrease.
Original value
£100.00
- Final value
- £120.00
v1.0 · Reviewed September 2026
How this is worked out
The final value is divided by the change factor: 1 plus the percentage for an increase, or 1 minus it for a decrease.
Worked example
- Final value £120
- 20%
- Increase
120 ÷ 1.2
£100.00
Assumptions and limits
- Subtracting the percentage from the final value is the common mistake. Taking 20% off £120 gives £96, not £100.
- A decrease of 100% or more cannot be reversed, because everything would have been removed, so no result is shown.