How to Calculate Discounts and Stacked Offers
The sale price formula, the real effect of “20% + 10%” offers and how to find a discount percentage.
During sales prices change fast and the real effect of an offer is hard to see. Two formulas cover it.
Sale price
Sale price = original price × (1 − discount). A 25% discount on 1,500 is 1,500 × 0.75 = 1,125, and you save 375.
Finding the discount rate
If you know the old and new price, rate = (old − new) ÷ old × 100. A product that fell from 800 to 600 is discounted (800 − 600) ÷ 800 = 25%.
Stacked discounts do not add up
“20% off, plus an extra 10% at checkout” does not mean 30%. The second discount applies to the reduced price: 1,000 × 0.80 × 0.90 = 720. The real discount is 28%.
Common mistakes
- Applying the percentage to the new price instead of the old one.
- Mixing VAT-inclusive and VAT-exclusive prices.
- Reading “up to 50% off” as everything being half price.
Use the Discount Calculator to try your own prices; the second tab handles stacked offers.