About the Reverse Percentage Calculator
A reverse percentage problem starts with the end result and asks for the starting point. A coat costs 75 after a 25 percent discount: what was the original price? A bill is 118 including 18 percent tax: what was the price before tax? The trick is that the percentage was taken from the original, not from the number you have now, so you divide by one plus or minus the percentage instead of adding or subtracting it. This calculator does the division for you, shows the original, and tells you how much was added or taken off.
Updated October 2026
How to use the Reverse Percentage Calculator
- 1Choose whether the percentage was taken off or added on.
- 2Enter the number you have now, such as the sale price.
- 3Enter the percentage that was applied.
- 4Read the original number and the amount that was added or removed.
- 5Check it by applying the percentage to the original.
The one rule to remember
If a number was multiplied by a factor, you undo it by dividing by that factor. A 20 percent discount multiplies by 0.8, so you divide by 0.8. A 20 percent rise multiplies by 1.2, so you divide by 1.2. The percentage always applies to the original value, which is why simple adding back goes wrong.
It also helps to know when the percentages stack. If a price was reduced by 20 percent and then a further 10 percent, the two steps multiply to 0.8 × 0.9 = 0.72, which is a 28 percent total reduction, not 30. To find the original price, divide by 0.72, or run the calculator twice, once for each step. The same care applies to a tax added on top of a discounted price: reverse them in the opposite order from the way they were applied.
Examples you may meet
- Shop sales: a jacket now costs 48 after a 40 percent discount, so the original was 80.
- Sales tax: a till receipt shows 53.50 with 7 percent tax, so the pre-tax price was 50.
- Tips: a restaurant total of 69 with a 15 percent tip means the meal cost 60.
- Salary: a pay rise of 5 percent that brought you to 31,500 means you earned 30,000.
Related tools
Use the Percentage Change Calculator when you have both numbers, the Discount Calculator to go forward from a price, the Sales Tax Calculator and VAT Calculator for tax sums, and the Tip Calculator when you are splitting a bill.
Features
- Works for discounts, tax, tips and increases
- Shows the amount added or taken off
- Explains the working in the result
- Catches impossible cases like a 100% discount
- Handles decimals
- Runs in your browser
Frequently asked questions
How do I find the original price after a discount?
Divide the sale price by one minus the discount as a decimal. If a coat costs 75 after a 25 percent discount, divide 75 by 0.75 to get an original price of 100.
How do I remove tax from a price?
Divide the total by one plus the tax rate. A 118 total with 18 percent tax gives 118 ÷ 1.18 = 100 before tax, and the tax paid was 18. Choose the added-on option in the calculator.
Why can't I just subtract the percentage from the new price?
Because the percentage was calculated on the original, not on the new number. Taking 25 percent off 75 gives 56.25, not 100. Dividing by the factor is the only correct way back.
Can I use this for a percentage increase?
Yes. If a rent rose by 10 percent to 1,100, divide by 1.10 and you get 1,000 as the old rent. Select added on, enter 1,100 and 10 percent.
What if the discount is 100 percent?
Then the sale price is zero whatever the original was, so the original cannot be recovered. The calculator tells you rather than returning a nonsense answer.
Is it the same as a percentage change calculator?
No. A percentage change calculator needs both numbers and returns the percent. A reverse percentage calculator needs the end number and the percent and returns the start.