About the Discount Calculator
Is “20% off plus an extra 10%” really 30% off? Is buy 2 get 1 free better than 30% off? This discount calculator answers the four questions shoppers ask most, and shows results as you type.
How to use
- In ①, enter the original price and the discount to see the sale price and how much you save. Tap a chip for common discounts.
- In ②, enter the original price and the price you actually pay to get the discount percentage.
- In ③, enter a first discount and an extra discount (coupon, card or loyalty offer) to see the real total discount.
- In ④, enter the price of one item to compare buy-1-get-1, buy-2-get-1 and similar deals with a percentage discount.
Discount formulas
| You want | Formula | Example |
|---|---|---|
| Sale price | price × (1 − discount ÷ 100) | $80 at 20% off → $64 |
| Discount % | (price − sale price) ÷ price × 100 | $120 → $84 = 30% |
| Stacked sale price | price × (1 − a) × (1 − b) | $200, 20% + 10% → $144 |
| Real stacked discount | 1 − (1 − a) × (1 − b) | 20% + 10% → 28% |
Sales tax is usually added at the register on top of the sale price.
Why stacked discounts add up to less
An extra discount applies to the already reduced price. $200 minus 20% is $160, and an extra 10% off takes only $16 more, so you pay $144. That is $4 more than a straight 30% off ($140), and the real discount is 28%, not 30%.
BOGO and multi-buy deals
| Deal | Pay for / get | Saving per item |
|---|---|---|
| Buy 1 get 1 free | 1 / 2 | 50% |
| Buy 2 get 1 free | 2 / 3 | about 33.3% |
| Buy 3 get 1 free | 3 / 4 | 25% |
| Buy 4 get 1 free | 4 / 5 | 20% |
“Buy one, get one 50% off” is only a 25% saving per item.
FAQ
What is 20% off plus an extra 10% off?
28% off. You pay 0.8 × 0.9 = 0.72, or 72% of the original price. That is 2 percentage points less than simply adding the two discounts.
Is buy 2 get 1 free better than 30% off?
Buy 2 get 1 free saves about 33.3% per item, so it is slightly better than 30% off, but only if you need all three items.
How do I calculate the percentage off from two prices?
Subtract the sale price from the original price, divide by the original price and multiply by 100. For $120 reduced to $84: 36 ÷ 120 × 100 = 30%.
Are my numbers saved?
Your last inputs are stored only in this browser so they are there when you come back. Nothing is sent to a server.