How the discount is worked out
Amount saved = Original price × Discount % ÷ 100. Subtract that from the original price to get your final sale price.
Example: A $80 item at 25% off saves you 80 × 25 ÷ 100 = $20, so you pay $60.
Stacking multiple discounts
Discounts don't add up the way you'd expect. A 20% discount followed by an extra 10% off is not 30% off overall — it's about 28% off, because the second discount applies to the already-reduced price, not the original. Always apply discounts one at a time, in order.
Worked example of stacked discounts
A $100 item with 20% off, then an extra 10% off at checkout:
- After first discount: 100 − (100 × 0.20) = $80
- After second discount: 80 − (80 × 0.10) = $72
- Total savings: $28, which is 28% off — not 30%
Working backward from the sale price
Sometimes you know the discounted price and the percentage, but want the original price. The formula is: Original price = Sale price ÷ (1 − discount ÷ 100). For example, if an item is $60 after a 25% discount: 60 ÷ (1 − 0.25) = 60 ÷ 0.75 = $80 original price.