How to calculate a discount
Sale price = price × (1 − discount ÷ 100)
A 30% discount on $120 is $120 × 0.70 = $84. You save $36.
Double discounts are not added together
"30% off, plus an extra 20% off" is a 44% discount, not 50%.
The second discount is taken from the already reduced price: $120 × 0.70 = $84, then $84 × 0.80 = $67.20. The combined discount is 1 − (0.70 × 0.80) = 0.44, or 44%. The order of the two discounts does not change the result.
| Deal | Combined discount |
|---|---|
| 20% + extra 10% | 28% |
| 30% + extra 20% | 44% |
| 50% + extra 20% | 60% |
| 50% + extra 50% | 75% |
Where tax fits in
In the US and Canada, sales tax is added at the till to the discounted price, so enter your rate to see the real total. In the UK and the Netherlands, shop prices already include VAT, so leave the tax field empty.
Pro-tip: compare a percentage discount with a fixed amount off by converting both to the final price. "$25 off $120" ($95) is a worse deal than "30% off" ($84).
Frequently asked questions
How do I calculate a percentage discount?
Multiply the price by 1 minus the discount as a decimal. 30% off $120 is $120 × 0.70 = $84.
How do two discounts combine?
Multiply the remaining fractions. 30% off and then 20% off leaves 0.70 × 0.80 = 0.56 of the price, which is a 44% discount overall.
How do I work out what percentage off I got?
Divide the amount saved by the original price and multiply by 100. Paying $84 for a $120 item saves $36, and $36 ÷ $120 × 100 = 30%.
Is tax calculated before or after the discount?
In the US and Canada, sales tax is normally charged on the discounted price. In the UK and the EU, displayed prices already include VAT.