Quick answer: A discounted price is the original price × (1 − discount ÷ 100). An $80 jacket at 25% off costs $60, and adding a second 10% off at checkout makes it $54, which is 32.5% off in total because the second discount applies to the reduced price.
Sales signs shout percentages, but what matters is the price you pay. This calculator turns “30% off” into a number, shows how much you save, and lets you add a second coupon and sales tax so the total matches the receipt.
It also works backwards. If you know the original price and the sale price, switch the mode and it tells you what percentage discount you are actually getting, which is handy for checking whether a deal is as good as it looks.
The formulas
Savings = original − sale price
Discount % = (original − sale) ÷ original × 100
Two discounts: original × (1 − d1) × (1 − d2)
When two discounts stack, the second is taken from the reduced price, not the original. 20% off followed by 10% off is a total of 28% off, not 30%. Sales tax is normally added after the discounts, so the tax is on the lower price.
A worked example
Example. An $80 jacket with 25% off costs $60. Add an extra 10% off at checkout and it becomes $54, so you save $26, which is 32.5% off in total. The two discounts are not added together because the second one applies to the already reduced price.
Common discounts on a $100 item
| Discount | You pay (on $100) | You save |
|---|---|---|
| 10% off | $90 | $10 |
| 20% off | $80 | $20 |
| 25% off | $75 | $25 |
| 30% off | $70 | $30 |
| 40% off | $60 | $40 |
| 50% off | $50 | $50 |
For any price, multiply by the “You pay” share, for example × 0.75 for 25% off.
Common mistakes to avoid
- Adding two discounts together. 20% off followed by 10% off is 28% off in total, not 30%.
- Applying sales tax before the discount. In most places tax is charged on the price after the discount.
- Judging a deal by the percentage alone. Compare final prices, since a large discount on an inflated price is not a bargain.
Frequently asked questions
How do I calculate a percentage discount?
Multiply the price by the discount rate as a decimal, then subtract. For 25% off $80: 80 × 0.25 = 20, and 80 − 20 = 60. Or multiply by 0.75 to get $60 in one step.
Why is a 20% then 10% discount not 30% off?
The second discount applies to the price after the first one, which is already lower. So you save 20% of the original, then 10% of the remaining 80%, which is 8%, giving 28% in total.
Is sales tax charged before or after the discount?
In most places tax is charged on the discounted price. Some coupons are treated differently, so check the receipt. The tax field here is applied after the discounts.
How can I find the original price from a sale price?
Divide the sale price by (1 − discount). If a coat costs $60 after a 25% discount, the original price was 60 ÷ 0.75 = $80.
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Sources and further reading
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