Calculate sale prices, stacked discounts, and final cost including tax
Quick Answer:A 20% + 10% stacked discount is NOT 30% off. On a $100 item, 20% off = $80, then 10% off that = $72. The real total discount is 28%, saving you $28 instead of $30.
Final Price (with tax)
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Price After Discounts (pre-tax)
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Stacked discounts are a common marketing tactic that sound better than they are. "Take an extra 20% off already 40% off" sounds like 60% off, but it is actually only 52% off. Always do the math before you buy. Also, be wary of inflated "original prices" - some retailers mark up the original price before a sale to make the discount seem larger. Compare the final price against competitor prices, not just the original price tag.
Stacked discounts are applied sequentially, not added together. A 20% discount on a $100 item brings it to $80. Then a 10% discount on $80 removes $8, giving you $72. That is a 28% total discount, not 30%. The second discount applies to the already-reduced price, so it removes less in absolute terms. This is why stacked discounts always total less than their sum.
Mathematically, the order does not matter for the final price. A 20% off then 10% off gives the same result as 10% off then 20% off (both equal 28% total). This is because multiplication is commutative: (0.80 x 0.90) equals (0.90 x 0.80). However, some stores may have specific rules about which discount applies first.
To find the original price, divide the sale price by (1 - discount/100). For example, if an item costs $60 after a 25% discount: $60 / (1 - 0.25) = $60 / 0.75 = $80 original price. You can verify: 25% of $80 = $20 discount, and $80 - $20 = $60.