A percent-off discount multiplies the price by what is left after the discount. 30% off means you pay 70% of the original price, so an $80 item costs $80 × 0.70 = $56. This discount calculator gives the sale price, the dollars saved, and the total after sales tax. It also handles stacked offers such as "an extra 20% off already-reduced items", which many shoppers assume add up to 50% off but don't.
Need a plain percentage instead? Use the percentage calculator. To compare a sale price with a regular price as a percentage, use the percent change calculator.
How to use the discount calculator
- Enter the original (ticket) price.
- Enter the percent off.
- If the store takes an extra percentage off the reduced price, enter it as the extra discount.
- Optionally enter your sales tax rate. Tax is applied to the discounted price, which is how most US states treat store discounts.
Formula
The overall discount for two stacked offers is 1 − (1 − d₁)(1 − d₂). For 30% then 20%: 1 − 0.7 × 0.8 = 0.44, so 44% off, not 50%.
Worked example
A jacket is $80, marked 30% off, with an extra 20% off at checkout and 8.25% sales tax.
- After 30% off: $80 × 0.70 = $56.00.
- Extra 20% off: $56 × 0.80 = $44.80.
- Savings: $80 − $44.80 = $35.20, which is 44% off in total.
- Tax: $44.80 × 0.0825 = $3.70, so the register total is $48.50.
Quick percent-off table
Multiply the original price by the "you pay" factor.
| Discount | You pay | On a $50 item | On a $120 item |
|---|---|---|---|
| 10% off | × 0.90 | $45.00 | $108.00 |
| 15% off | × 0.85 | $42.50 | $102.00 |
| 20% off | × 0.80 | $40.00 | $96.00 |
| 25% off | × 0.75 | $37.50 | $90.00 |
| 30% off | × 0.70 | $35.00 | $84.00 |
| 40% off | × 0.60 | $30.00 | $72.00 |
| 50% off | × 0.50 | $25.00 | $60.00 |
| 75% off | × 0.25 | $12.50 | $30.00 |
Is the "original price" real?
A discount is only as meaningful as the price it is measured from. The US Federal Trade Commission's Guides Against Deceptive Pricing (16 CFR Part 233) say a former-price comparison is fair when the former price is one at which the item was openly and actively offered for a reasonably substantial period, and they warn against inflated "was" prices created only to advertise a large reduction. If you are deciding whether a deal is good, compare the sale price with what the same item sells for elsewhere, not only with the tag.
Order matters for coupons: a fixed-dollar coupon applied before a percentage discount saves less than the same coupon applied after it. Percentage discounts can be applied in either order with the same result.
Caveats and assumptions
- Sales tax rules vary by state and city, and some items are exempt or taxed on the pre-coupon price. Check your local rules.
- Results are rounded to the cent; stores may round each step slightly differently.
- Discounts above 100% are rejected.
- Store prices in examples are illustrative.
Frequently asked questions
How do I calculate 30% off?
Multiply the price by 0.70. For $80: $80 × 0.70 = $56. The savings are $80 × 0.30 = $24.
Is 20% off plus an extra 20% off the same as 40% off?
No. You pay 0.8 × 0.8 = 0.64 of the price, which is 36% off in total.
How do I find the original price from the sale price?
Divide the sale price by the fraction you paid. A $56 sale price at 30% off came from $56 ÷ 0.70 = $80.
Is sales tax charged before or after the discount?
In most US states, a store’s own discount reduces the taxable price, so tax is charged on the sale price. Manufacturer coupons are sometimes treated differently, so check your state’s rules.
How do I work out what percent off a sale is?
Divide the savings by the original price and multiply by 100. $24 saved on $80 is 24 ÷ 80 × 100 = 30% off.
Sources
- OpenStax Prealgebra 2e — 6.3 Solve Sales Tax, Commission, and Discount Applications — discount and sale price formulas
- eCFR — 16 CFR Part 233, Guides Against Deceptive Pricing (FTC) — former price comparisons
- OpenStax Prealgebra 2e — 6.1 Understand Percent — percent to decimal conversion
This calculator gives estimates for planning and education. Check measurements, local codes, supplier specs and your school's official policy before relying on a result. See our disclaimer and how we build and check calculators.