Whether you’re a shopper checking a deal or a store owner setting a promotion, knowing how to calculate a discount quickly saves money and avoids mistakes at the till.
TL;DR: To find a sale price, multiply the original price by (1 − discount ÷ 100). A $80 item at 25% off costs $80 × 0.75 = $60. The amount you save is original price × discount ÷ 100. Try our Discount Calculator to do it instantly.
The discount formula
There are two numbers people usually want: the amount saved and the final price.
Amount saved = Original price × (Discount % ÷ 100).
Sale price = Original price − Amount saved, which is the same as Original price × (1 − Discount % ÷ 100).
Example: a jacket is $120 with 30% off. Amount saved = 120 × 0.30 = $36. Sale price = 120 − 36 = $84.
Working backwards from a sale price
Sometimes you see the final price and want to know the discount. If something dropped from $50 to $35, the discount rate is (50 − 35) ÷ 50 = 0.30, or 30% off. To recover the original price from a sale price and a known discount, divide: original = sale price ÷ (1 − discount ÷ 100). So $84 at 30% off came from 84 ÷ 0.70 = $120.
Stacking discounts the right way
A common mistake is adding two percentages together. “20% off, then an extra 10%” is not 30% off. You apply them one after another: $100 × 0.80 = $80, then $80 × 0.90 = $72 — an effective discount of 28%, not 30%. Multiply the factors rather than summing the percentages.
Don’t forget tax
Discounts are normally applied before sales tax, so calculate the sale price first, then add tax on the reduced amount. Our Sales Tax Calculator handles that step, and the Percentage Calculator is handy for any “what percent of” question.
Frequently asked questions
How do I calculate 15% off?
Multiply the price by 0.85. A $40 item at 15% off is 40 × 0.85 = $34. The amount saved is 40 × 0.15 = $6.
Is 20% off then 20% off the same as 40% off?
No. Two successive 20% discounts give 0.8 × 0.8 = 0.64, an effective 36% off — not 40%. Stacked percentage discounts always multiply.
How do I find the original price before a discount?
Divide the sale price by (1 minus the discount as a decimal). A $45 price after a 25% discount came from 45 ÷ 0.75 = $60.
Sources
Based on standard percentage and retail-pricing arithmetic. Figures are illustrative examples; always confirm a store’s exact terms, as some discounts exclude tax, shipping, or already-reduced items.