Reverse Percentage Calculator
This reverse percentage calculator works backwards from a price after a discount, VAT or markup to find the original figure.
Formula & worked example
Formula: Original = final ÷ (1 + p ÷ 100) after an increase, or final ÷ (1 − p ÷ 100) after a discount.
Example: 80 after a 20% discount: 80 ÷ 0.80 = 100. 120 including 20% VAT: 120 ÷ 1.20 = 100.
Method & source: Inverse of the multiplier method: final ÷ (1 ± p ÷ 100). See how we test our calculators.
Next step: try adding and removing VAT or percentage increase and decrease or price per unit.
What Is a Reverse Percentage Calculator?
This kind of tool works backwards from a final amount to the original one. If a jacket costs 80 after a 20% discount, or an invoice totals 120 after 20% VAT, this tool tells you the price before that change.
The common mistake is to take 20% off the final figure. That gives the wrong answer because the percentage was applied to the original amount, not the final one.
How Our Reverse Percentage Calculator Works
Enter the final value, the percentage and whether it was an increase (such as tax or markup) or a discount.
- After an increase: Original = final ÷ (1 + percent ÷ 100).
- After a discount: Original = final ÷ (1 − percent ÷ 100).
- Amount changed: The exact amount added or taken off.
- Working shown: The formula with your numbers so you can verify it.
- Proof check: The original is put through the percentage again to confirm the final value.
The proof line at the bottom makes it easy to trust the result before you use it in a quote or price list.
Why Reversing a Percentage Matters
Prices you see are often the finished figure, but decisions depend on the starting point.
- Find the price before VAT or sales tax was added.
- Discover the original price before a sale discount.
- Check whether a “70% off” offer is genuinely as good as it looks.
- Work out pre-raise salaries or pre-increase rents.
- Strip a service charge or markup out of a total.
With a reverse percentage calculator you can find the original price before an increase or discount without guessing or trial and error.
Worked walkthrough: a sale price
A television is on sale for 360 after a 25% discount. Because 360 is 75% of the original price, the original is 360 ÷ 0.75 = 480, and the discount saved 120. Taking 25% off 360 would wrongly give 270, which is why the divide-by-multiplier method matters. The same approach removes tax: a total of 120 that includes 20% VAT is 120 ÷ 1.20 = 100 before tax, with 20 of VAT. The calculator finishes with a proof line, multiplying the original by the multiplier to reproduce the final price.
Practical tips for reverse percentage calculations
- Choose “after a discount” when the price went down and “after an increase” for tax, markup or service charges added on top.
- For sales tax or VAT, enter the tax rate as the increase. The tool divides by 1 plus the rate to strip it out.
- If a price was reduced twice, work backwards one step at a time, starting with the last reduction.
- A discount of 100% or more cannot be reversed – the original would be undefined – so the tool asks you to check the figure.
- Use the proof line to double-check results before you put a number into a quote, receipt or spreadsheet.
Frequently Asked Questions (FAQs)
Divide the sale price by (1 − discount ÷ 100). If a coat costs 80 after 20% off, 80 ÷ 0.8 = 100 was the original price.
Choose “Increase” and enter the tax rate. The calculator divides the total by 1 plus the rate, giving the price before tax and the tax amount.
Because the percentage was calculated on the original price. Subtracting 20% of 120 gives 96, but the real pre-tax price is 100.
The original price cannot be recovered from a final price of zero, so the calculator warns you that a discount of 100% or more cannot be reversed.
Yes. Both the final value and the percentage accept decimals, such as 12.5%.