Percentage guide
Reverse Percentage Calculator
A reverse percentage calculation finds the original value when you know the final amount after a percentage change. It helps when a sale price, tax-inclusive total, or increased figure is known but the starting amount is not.
Work backwards from a percentage change
Enter the final value, the percentage change, and whether it was an increase or decrease.
The interactive calculator loads with the page so you can enter your own values and see the result instantly.
How to calculate reverse percentage
Do not subtract the percentage directly from the final amount. First convert the percentage to the multiplier that created the final value, then divide by that multiplier.
Formula: original value = final value ÷ (1 ± percentage ÷ 100)
- Turn the percentage into a decimal and add it to 1 for an increase, or subtract it from 1 for a decrease.
- Divide the final value by this multiplier.
- The result is the value before the percentage change.
Example: $90 after a 10% discount
A 10% discount means the final price is 90% of the original, or 0.90. Divide $90 by 0.90 to get $100, the original price.
Common questions
How do you reverse a percentage increase?
Divide the final value by 1 plus the increase as a decimal. If 120 includes a 20% increase, calculate 120 ÷ 1.20 = 100.
Related percentage calculators
Use a focused calculator when your question needs a different baseline or a price-specific formula.
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Measure how much a value has grown from its starting point.
Percentage Decrease Calculator
Work out the percentage reduction from an original value.
Percentage Difference Calculator
Compare two values when neither one is the original baseline.
Discount Calculator
Calculate the amount saved and the final sale price.
VAT Calculator
Add VAT to a net price or remove it from a gross total.