Reverse Percentage Calculator
Reverse percentage calculator for 2026 price and discount math. Enter a final value and percentage change to recover the original amount before an increase or decrease.
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Result
Enter values above and click Calculate to see your result.
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Formula
How it works: To reverse a percentage increase, divide the final value by 1 plus the percentage as a decimal. To reverse a percentage decrease, divide by 1 minus the percentage as a decimal.
Worked Example
How Reverse Percentage Works
Reverse percentage starts with the final number and works backward to the original amount before a price rise, tax addition, discount, or fee reduction was applied.
- Use divide, not subtract, when undoing a percentage change
- A 20% discount means divide by 0.80 to recover the original price
- A 10% tax-inclusive total means divide by 1.10 to recover the pre-tax amount
- This is useful for sale prices, wage increases, fees, and markups
If you know the final total but not the starting amount, reverse percentage gives you the missing original value.
You can also calculate changes using our Percentage Calculator, Percentage Increase Calculator, Percentage Decrease Calculator or Discount Calculator.
Frequently Asked Questions
How do I find the original price before a discount?
Divide the sale price by 1 minus the discount as a decimal. For example, a $120 sale price after 20% off means the original price was $120 / 0.80 = $150.
How do I reverse a price increase?
Divide the new price by 1 plus the increase rate. If a price rises 25% to $250, the original amount was $250 / 1.25 = $200.
Why can I not just subtract the percentage?
Because percentage math is multiplicative. The final amount already includes the change, so you need to divide by the full multiplier to recover the starting number correctly.
Can I use this for tax-inclusive prices?
Yes. Treat tax as an increase. A $110 total including 10% tax means the pre-tax subtotal was $110 / 1.10 = $100.
Is reverse percentage the same as percentage decrease?
No. Percentage decrease measures how much a value fell. Reverse percentage starts with the final amount and works backward to the original value before the change.
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