Reverse Percentage Calculator
You know the final price and the percentage that was added or removed — this finds what the number was before.
Last updated
How to find the original price before a percentage change
- Type the final value, for example the sale price
85. - Choose whether it came after a decrease (discount) or an increase (markup or tax), and type the percentage.
- The original value appears straight away: £85 after a 15% discount was £100.
The formula
For a decrease: original = final ÷ (1 − percentage ÷ 100)
For an increase: original = final ÷ (1 + percentage ÷ 100)
Common use: a shirt costs $85 after a 15% discount — what was the original price? Answer: $85 ÷ 0.85 = $100.
Questions about reverse percentages
How do I find the original price before a discount?
Divide the sale price by 1 minus the discount as a decimal. After 20% off, £60 was £60 ÷ 0.8 = £75 to begin with.
How do I remove VAT or tax from a price?
Divide the price including tax by 1 plus the rate as a decimal. With 20% VAT, £120 is £120 ÷ 1.2 = £100 before VAT.
Why can’t I just take the percentage off the final price?
Because the percentage was worked out on the original price, not the final one. Taking 20% off £120 gives £96, not the £100 it was before 20% was added.
Does it work for any percentage?
Yes, for increases of any size and decreases below 100%. A decrease of 100% or more leaves nothing, so the tool explains that the original can’t be worked out.