Discount Calculator
20% off 100 leaves 80. Stacking 20% and 10% takes 28% off, so you pay 72, not 70. A price of 80 after 20% off was 100 before.
How to use
- On "Sale price", enter the original price and the discount percentage. Add a second or third discount if the offers stack.
- Read the final price, the amount you save and the real total discount. For stacked offers the steps are listed one by one.
- Use "Price before discount" if you know the sale price and the percentage off, or "Discount rate" if you know both prices.
How it works
Sale price = original × (1 − discount ÷ 100). For example 100 with 20% off is 100 × 0.80 = 80, so you save 20.
Stacked discounts multiply: final = original × (1 − d1) × (1 − d2) × (1 − d3). Real total discount = 1 − (1 − d1)(1 − d2)(1 − d3).
20% + 10% is therefore 1 − 0.80 × 0.90 = 28%, not 30%. The second discount works on a smaller price.
Original price from a sale price = sale price ÷ (1 − discount ÷ 100). 80 after 20% off gives 80 ÷ 0.80 = 100.
Discount rate = (original − sale price) ÷ original × 100. The order of stacked discounts does not change the final price, because multiplication does not depend on order.
Why 20% + 10% is not 30%
Each discount applies to the price left after the one before it. Take 20% off 100 and you pay 80. Then take 10% off 80, which is 8, and you pay 72. The total discount is 28, not 30.
The table shows the real combined discount next to the figure you get by simply adding the percentages. Two discounts of 50% do not give a free item: 100 becomes 50, then 25.
| Original price | Discounts | Final price | Real total discount | Added up |
|---|---|---|---|---|
| 100 | 20% | 80 | 20% | 20% |
| 100 | 20% + 10% | 72 | 28% | 30% |
| 100 | 50% + 50% | 25 | 75% | 100% |
| 200 | 30% + 20% + 10% | 100.8 | 49.6% | 60% |
| 80 | 15% + 15% | 57.8 | 27.75% | 30% |
Finding the price before the discount
If an item is 80 after 20% off, the original price is not 80 + 20%. The 20% was taken from the original, so original = 80 ÷ (1 − 0.20) = 100. Adding 20% to 80 would give 96, which is wrong.
Finding the discount rate
Discount % = (original − sale price) ÷ original × 100. From 100 down to 80 is 20%. A sale price above the original gives a negative rate, which is a price increase.
Rounding
Prices are shown to two decimal places but the calculation keeps full precision, so a long chain of discounts does not pile up rounding errors. Shops usually round each step, so a checkout total can differ by a cent.
FAQ
Is 20% off plus 10% off the same as 30% off?
No. The second discount applies to the already reduced price. 20% then 10% gives a total discount of 28%, so on 100 you pay 72 rather than 70.
How do I check a Black Friday "extra 10% off" deal?
An extra 10% off an item already 30% off is a stacked discount: 0.70 × 0.90 = 0.63, so you pay 63% of the original price, a 37% total discount, not 40%. Enter 30 and 10 as the first and second discount. Black Friday 2026 is on Friday, November 27, and Cyber Monday on November 30. In Google Trends (2021 to 2026), US searches for discount calculators peak in that week.
Does the order of the discounts matter?
No. 10% then 20% gives the same final price as 20% then 10%, because you multiply the same factors (0.90 and 0.80) either way.
How do I find the original price from the sale price?
Divide the sale price by 1 minus the discount as a fraction. For 20% off, divide by 0.80. Adding 20% on top of the sale price gives the wrong answer.
How do I calculate the percentage off between two prices?
Subtract the sale price from the original, divide by the original and multiply by 100. From 59.99 to 41.99 is about 30% off.
What if the discount is a fixed amount, not a percentage?
Subtract it directly: 100 minus a 15 coupon is 85. To see what that is as a percentage, use the Discount rate mode with 100 and 85.
Does it work in any currency?
Yes. Enter plain numbers in one currency; the result uses the same unit.