Reverse Percentage Calculator
Work backward from a value after an increase or decrease, or find a whole when the known value is a stated percentage of it. The forward calculation verifies the answer.
Written and checked by TheToolNet Editorial Team · Last reviewed: September 20, 2026 · Editorial method
Find the original value
Reverse percentage formulas
| Known situation | Original value |
|---|---|
| After p% increase | final ÷ (1 + p/100) |
| After p% decrease | final ÷ (1 − p/100) |
| Known value is p% of whole | part ÷ (p/100) |
If a price rose 20% to 120, the original was 120 ÷ 1.2 = 100. Subtracting 20% from 120 would give 96, which is wrong because that decrease uses 120 rather than the original 100 as its base.
Frequently asked questions
How do I reverse a discount?
Divide the sale price by one minus the discount rate. A 25% discount leaves a multiplier of 0.75.
Can a 100% decrease be reversed?
No. Every original value becomes zero after a complete decrease, so the original cannot be recovered from zero alone.
How do I compare two known values?
Use the percentage change calculator.