How to Calculate a Discount and Sale Price
A “% off” sign is easy to misjudge. Here’s how to turn any discount into the real saving and final price, plus a couple of mental tricks for the shop.
The basic formula
Saving = original price × (discount% ÷ 100). Final price = original − saving, or more directly: original × (1 − discount ÷ 100). So a $80 jacket at 25% off is 80 × 0.75 = $60, saving $20.
The Discount Calculator does this instantly and shows both the saving and the final price.
Mental shortcuts
For 10%, move the decimal one place left ($80 → $8). For 20%, double that ($16). For 25%, take a quarter (divide by 4). For 50%, halve it. Combine them: 30% = 10% × 3.
Stacked and double discounts
Two discounts don’t simply add. “30% off, then an extra 20%” is 0.70 × 0.80 = 0.56, i.e. 44% off — not 50%. Apply them one after another, and watch whether tax is added before or after the discount.
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Last updated: July 6, 2026