Reverse Percentage Calculator
Find the original number before a percentage increase or decrease was applied.
Inputs
The percent that was added or removed.
Original Value
100.0000
Multiplier Used
1.2000
Step by step
Determine the multiplier
1 + 20/100 = 1.2
= 1.2
Divide final value by multiplier
120 ÷ 1.2
= 100.000000
How it works
If a value was increased by P%, the final equals original × (1 + P/100). To reverse this, divide the final by that factor. Similarly, for a decrease divide by (1 − P/100).
Formulas
Reverse Percentage (increase)
Original = Final / (1 + P/100)
- Final
- The value after the increase
- P
- The percentage that was applied
Reverse Percentage (decrease)
Original = Final / (1 − P/100)
- Final
- The value after the decrease
- P
- The percentage that was applied
Frequently Asked Questions
Why can't I just subtract the percentage from the final value?
Because the percentage was applied to the original, not the final. For example, 20% of 100 is 20, giving 120. But 20% of 120 is 24, not 20. You must divide, not subtract.
What is a practical use case?
Finding the pre-tax price: if an item costs $120 including 20% VAT, the pre-tax price is 120 / 1.20 = $100.