Reverse percentage means working backwards from a final value to find the original value. It is useful when a value has already been increased, decreased, discounted, taxed, or changed by a percentage, and you want to know what the starting number was.
Use the calculator to check the number quickly, then read the guide for formulas, examples, and common mistakes.
What Is Reverse Percentage?
Reverse percentage is used when the final value is known but the original value is missing.
For example, if a product is now 80 after a 20% discount, reverse percentage helps find the original price.
It is called reverse percentage because you are undoing a percentage change.
Reverse Percentage After a Decrease
When a value has decreased by a percentage, the final value represents the remaining percentage.
For example, after a 20% decrease, the final value is 80% of the original value.
The formula is: original value = final value ÷ (1 - percentage decrease ÷ 100).
Example: Original Price Before Discount
Suppose the sale price is 80 after a 20% discount.
The remaining percentage is 80%, or 0.80.
Original price = 80 ÷ 0.80 = 100.
Reverse Percentage After an Increase
When a value has increased by a percentage, the final value is more than 100% of the original value.
For example, after a 25% increase, the final value is 125% of the original value.
The formula is: original value = final value ÷ (1 + percentage increase ÷ 100).
Example: Original Value Before Increase
Suppose a price is now 150 after a 25% increase.
The final value represents 125% of the original value, or 1.25.
Original value = 150 ÷ 1.25 = 120.
Reverse Percentage vs Adding the Percentage Back
A common mistake is adding the percentage back to the final value.
For example, if 80 is after a 20% discount, adding 20% to 80 gives 96, not 100.
That is wrong because the 20% discount was based on the original price, not the sale price.
Reverse Percentage for Discounts
Discounts are one of the most common reverse percentage uses.
If the sale price is known and the discount percentage is known, the original price can be found by dividing by the remaining percentage.
For a discount-specific guide, read How to Find Original Price Before Discount.
Reverse Percentage for Tax or Fees
Reverse percentage can also help when tax or fees are already included in a final amount.
For example, if a final price includes 10% tax and the total is 110, the pre-tax amount is 110 ÷ 1.10.
The result is 100, because 100 plus 10% equals 110.
Reverse Percentage for Growth
If a number grew by a percentage and you know the new value, divide by the growth multiplier.
For example, if revenue is now 12,000 after a 20% increase, the original revenue was 12,000 ÷ 1.20.
The result is 10,000.
Reverse Percentage for Decrease
If a number fell by a percentage and you know the new value, divide by the remaining percentage.
For example, if traffic is now 7,500 after a 25% decrease, the final value is 75% of the original value.
Original traffic was 7,500 ÷ 0.75, which equals 10,000.
Common Mistakes to Avoid
The first mistake is adding the percentage back instead of dividing by the correct multiplier.
The second mistake is using the same formula for increases and decreases.
The third mistake is forgetting that the final value represents either more than 100% or less than 100% of the original value.
Use the Calculator
Use the Percentage Calculator to check related percentage calculations.
For percentage increase, read Percentage Increase Formula.
For percentage decrease, read Percentage Decrease Formula.
Conclusion
Reverse percentage helps find the original value before a percentage change.
For a decrease, divide by the remaining percentage. For an increase, divide by the increased percentage multiplier.
Related guides and tools
FAQs
What is reverse percentage?
Reverse percentage means working backwards from a final value to find the original value before a percentage change.
How do I reverse a 20% discount?
Divide the sale price by 0.80 because the sale price is 80% of the original price.
How do I reverse a 25% increase?
Divide the final value by 1.25.
Why is adding the percentage back wrong?
Because the original percentage change was based on the original value, not the final value.