How to calculate a sale price
Sale price = original × (1 − discount ÷ 100)
For 30% off $120: 120 × 0.70 = $84, saving $36.
Stacked discounts
Stores often offer an extra discount on top of a sale, such as "an extra 10% off sale items". These apply one after another, not added together:
- 30% off $120 → $84
- Extra 10% off $84 → $75.60
- Total saved: $44.40, which is 37% off, not 40%
Is it a good deal?
- Check the original price. A big "percent off" means little if the starting price was inflated.
- Compare per unit. For groceries and household items, the price per ounce or per item tells you more than the discount.
- Count the tax. Sales tax is usually charged on the discounted price, so add it to see what you will really pay.
- Mind "buy one, get one 50% off". That is 25% off each item when you buy two.
Working out tax on a purchase? Try the sales tax calculator.
Last reviewed October 2026.
Frequently asked questions
How do I calculate a discount?
Multiply the original price by the discount percentage divided by 100 to get the amount saved, then subtract it. 30% off $120 is 120 × 0.30 = $36 saved, so you pay $84.
Is 20% off plus an extra 10% off the same as 30% off?
No. Stacked discounts apply one after the other. 20% off $100 is $80, then 10% off $80 is $72, a total of 28% off, not 30%.
How do I find the percentage off from the sale price?
Divide the amount saved by the original price and multiply by 100. A $60 item on sale for $45 saves $15, and 15 ÷ 60 × 100 = 25% off. Use the second box on this page.
Is sales tax charged before or after the discount?
In most US states, sales tax is charged on the discounted price you actually pay. Manufacturer coupons can be treated differently in some states.
How do I find the original price before a discount?
Divide the sale price by (1 − discount ÷ 100). If an item costs $84 after 30% off, the original price was 84 ÷ 0.70 = $120.