Example 1
If 125 comes after a 25% increase, the original value was 100.
Quick Tool Labs
Reverse Percentage Calculator
Use this reverse percentage calculator to work backward from a final value and a percentage change. It estimates the original value before an increase or decrease was applied.
Calculator
Original value
0
Percentage amount
0
Adjusted value
0
Enter the adjusted value and percentage change to estimate the original starting value.
How this reverse percentage calculator works
This calculator works backward from a final adjusted value. If the value came after a percentage increase, it divides by one plus the percentage as a decimal. If it came after a decrease, it divides by one minus the percentage as a decimal.
Original value = adjusted value / (1 +/- percentage / 100)
Use it to estimate original prices before discounts, original salaries before raises, or starting values before a percentage-based adjustment.
Examples
Example 2
If 80 comes after a 20% decrease, the original value was 100.
Example 3
If a sale price is 72 after a 10% discount, the original price was 80.
Frequently asked questions
When should I use reverse percentage?
Use it when you know the final adjusted value and the percentage change, but you need to recover the original starting number.
What if the percentage is zero?
The original value is the same as the adjusted value because no change was applied.
Are there invalid percentage values?
Yes. A decrease of 100% or more makes the reverse calculation invalid because the denominator becomes zero or negative.