Discount Calculator
Calculate final sale price, dollar savings, and percentage off for any item.
Enter price and discount percentage, or reverse-calculate from the final price.
A discount calculator finds the sale price after a percentage reduction, or reverse-calculates the original price when you know the sale price and discount percentage.
The formulas:
Sale price from original and discount: Sale price = Original price × (1 − Discount% / 100) Discount amount = Original price × (Discount% / 100)
Original price from sale price and discount: Original price = Sale price / (1 − Discount% / 100)
Worked examples:
Example 1 — Simple discount: Original price: £120, discount: 25% Discount amount = £120 × 0.25 = £30 Sale price = £120 − £30 = £90
Example 2 — Stacked discounts: £150 item, first 20% off, then additional 10% off. After first discount: £150 × 0.80 = £120 After second discount: £120 × 0.90 = £108 Total saving: £42 (28% overall, NOT 30%)
Stacked discounts do not add — they multiply.
Example 3 — Reverse calculation: Sale price £84, was 30% off. What was the original? Original = £84 / (1 − 0.30) = £84 / 0.70 = £120
Common discount traps:
- “Buy 3 for the price of 2” = 33.3% off (not the advertised “save £X”)
- “Half price” must mean at least 28 days at full price (UK ASA rules)
- “Up to 70% off” means only some items are 70% off — most are less
Black Friday tip: Track prices before November — many “Black Friday” discounts start from an artificially inflated price set in the weeks before the sale.
Sale price vs markdown: Retail uses “markdown” to mean the absolute reduction in £. “Discount” typically means the percentage. £30 markdown on £120 = 25% discount.