1. Identify the change
A 20% discount leaves 80% of the original. A 20% increase makes the final amount 120% of the original.
Reverse percentage calculator
Local calculationUse the rate applied to the original amount.
Example answer
1,000
Original amount
Amount saved
200
Same units as your input
Original: 1,000 before a 20% discount.
Displayed results use your chosen decimal precision.
See the calculation
800 ÷ (1 − 20 ÷ 100) = 1,000
Check: 1,000 × 0.8 = 800
Live resultsNo sign-upNumbers stay in your browser
Work backwards from the final amount
How to calculate a reverse percentage
A reverse percentage calculation finds the original amount when you know the final amount and the percentage increase or decrease applied to it. Choose Before discount or Before increase, then enter the amount after the change and the rate applied to the original.
Before a discount: original = final ÷ (1 − discount ÷ 100)
Before an increase: original = final ÷ (1 + increase ÷ 100)
2. Divide by the multiplier
Convert the remaining percentage to a decimal. For a 20% discount, divide the final amount by 0.8. For a 20% increase, divide it by 1.2.
3. Check forwards
Apply the original change to your recovered amount. An original of 1,000 with 20% off gives 1,000 × 0.8 = 800.
Adding the discount rate back to the sale price does not undo the discount. Adding 20% to 800 gives 960, because that 20% is calculated on 800. To recover the original 1,000, divide 800 by the remaining 80% instead.
Load an example
Reverse percentage examples
Price before a discount
An item costs 800 after a 20% discount. Its original price was 800 ÷ 0.8 = 1,000, and the amount saved was 200.
Try the discount exampleAmount before an increase
An amount is 1,200 after a 20% increase. The original was 1,200 ÷ 1.2 = 1,000, with 200 added.
Try the increase exampleBefore a stated percentage charge
A total of 1,180 includes a simple 18% charge on the original amount. The original was 1,180 ÷ 1.18 = 1,000. The added charge was 180.
Try the included-charge exampleThese examples work in any currency or unit when both amounts use the same unit. Enter numbers without a currency symbol. For an included tax or charge, use the actual rate and check that it was applied as a single percentage of the original amount; this tool does not determine tax rates or billing rules.
Which percentage calculator do you need?
| What you know | What you need | Use |
|---|---|---|
| Final amount and the rate applied to the original | Original amount | This reverse percentage calculator |
| Original and final amounts | Percentage increase or decrease | Percentage change calculator |
| A percentage and an amount | That percentage of the amount | Percentage calculator |
When you already have both amounts, use the percentage change calculator to find the rate. Use our percentage calculator to find a percentage of a number or work out what percent one amount is of another. Those questions use different formulas from recovering an original amount.
Reverse percentage questions
Can I reverse a 100% discount?
No unique original can be recovered. A 100% discount turns every non-negative original amount into zero, so the final zero does not tell you the starting amount. This calculator requires a discount below 100%.
Can the increase be greater than 100%?
Yes. A 150% increase makes the final amount 250% of the original. If the final amount is 250, the original is 250 ÷ 2.5 = 100.
What happens with a zero amount or zero rate?
A zero rate leaves the amount unchanged. For an allowed rate, a final amount of zero recovers an original of zero. Negative amounts and negative rates are not accepted by this tool; choose the other mode to change the direction.
Can I reverse two successive discounts?
Reverse them one at a time, or use their combined multiplier. Two 10% discounts leave 0.9 × 0.9 = 0.81 of the original, so they are equivalent to a 19% discount, not 20%. Enter 19% here to reverse that combined discount.
Why is the displayed check approximate?
The calculator uses ordinary browser number arithmetic. Display rounding does not change the internal calculation, but very long decimals or extreme values can lose precision. The forward check uses the unrounded recovered amount. Choose up to 0, 2, 4 or 8 decimal places for the displayed result.
Are my numbers stored?
The calculation runs in your browser. Entered numbers are not sent for calculation, and the tool does not save a calculation history. Copy answer places the result on your clipboard only when you select it.