Reverse percentage calculator
Recover an original value from a final value and a known percentage change. Enter a negative percentage for a decrease.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| Final value | Enter final value using the definition in the method and example. |
| Percentage change (%) | Enter percentage units: 5 means 5%, not a fraction of 0.05. |
Understanding your result
Read Original value in the units and model stated on this page. The formula original = final ÷ (1 + p/100) defines the relationship; measurement accuracy and model applicability are separate from numerical precision.
Common mistakes
- Mixing input units or changing the physical meaning of a variable without changing the model.
Check your calculation
- Use the worked example as a known reference case, then change one input at a time and check the direction and units of the response.
Calculation checks, sources and review limits
What was the original value before a percentage increase or decrease?
Enter the final value and percentage change to work backwards to the original. A percentage decrease is entered as a negative number.
Common uses
- Recover a pre-discount price.
- Find the value before a known percentage increase.
How it works
A percentage change multiplies the original value by 1 + p/100. Divide the final value by this multiplier to recover the original. A −100% change reduces every original value to zero, so it cannot be reversed uniquely.
Worked example
A final price of 80 after a 20% decrease had an original price of 80 ÷ 0.8 = 100.