🏷️ Discount Calculator

Two discounts that stack multiply, they do not add: 30% off then 20% off is 44% off, not 50%. This page applies the second coupon to the reduced price (which is how checkout actually works) and prints the equivalent single percentage so the advertising maths stops lying to you.

Stacked discounts are multiplication

Every percentage-off is a retention factor: 30% off keeps 0.70 of the price. Coupons that apply after the sale multiply the factors — order does not matter, but addition does not work. If a store advertises "50% off everything, plus an extra 20% at checkout", the real factor is 0.50 × 0.80 = 0.40: 60% off. The table above shows that in cents, which is harder to argue with than in percentages.

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