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How Do Stacked Discounts Work? Successive Percentage Discounts Explained

Written by Muhammad Ajmal · Last reviewed 2026-08-29

When a store offers 20% off and you stack a 10% off coupon on top, the combined saving is not 30%. Each discount applies to whatever price is left after the one before it, so the two together only save 28%. Run any pair of numbers through our discount calculator one step at a time to check this against your own receipt, or work through the logic below.

Why percentages don't simply add together

A percentage discount is a multiplier, not a flat subtraction. Taking 20% off a price means multiplying it by 0.80. A second 10% discount then multiplies that new, already-reduced price by 0.90. Multiply the two factors together and you get 0.80 times 0.90, which equals 0.72, meaning you pay 72% of the original price. That is a 28% total saving, not 30%.

The gap between the two numbers grows as the discounts get bigger. Two separate 50% discounts stacked together do not clear the whole price. They leave you paying 0.50 times 0.50, which is 0.25, or 25% of the original price, a 75% total saving rather than the 100% off that naive addition would suggest.

Worked example with real numbers

Take a $150 jacket marked down 25%, with an extra 15% off applied at checkout.

• Step one: $150 x 0.75 = $112.50
• Step two: $112.50 x 0.85 = $95.63
• Total saved: $150 minus $95.63 = $54.37

As a single percentage, $54.37 off $150 works out to a 36.2% total discount, not the 40% you'd get by adding 25 and 15 together. Reversing the order of the two discounts gives the identical final price, since multiplication does not care which factor comes first.

The formula for any number of stacked discounts

For two discounts expressed as decimals, the combined multiplier is (1 minus discount one) times (1 minus discount two). Subtract that result from 1 and you have the true combined percentage off. The same pattern extends to three or more discounts: multiply all the leftover-price factors together, then subtract from 1. A 10%, 10% and 10% stack, for instance, works out to 1 minus (0.90 x 0.90 x 0.90), which is about 27.1% off, not 30%.

When retailers apply discounts differently

Not every store stacks discounts sequentially. Some retailers add percentages together before applying them once, which does produce a flat 30% off in the 20-plus-10 example above. Others cap the combined saving, exclude certain items from a second discount, or apply a coupon to the pre-tax subtotal only. Store policy determines which method is used, so the receipt is the only reliable way to confirm which approach was used on a given purchase; the math above tells you what to expect under the standard sequential method most checkout systems use.

Percentage off versus a fixed dollar coupon

A fixed dollar coupon, such as $10 off, behaves differently from a percentage discount when stacked. Applying a percentage discount first and then subtracting a flat dollar amount gives a different final price than subtracting the dollar amount first and then applying the percentage, because the percentage in the second case is calculated on a smaller base. When both a percentage and a flat coupon are available, check the checkout total under each possible order rather than assuming the outcome is the same either way.

Checking your own math

Because each discount depends on the price left over from the last one, the fastest way to verify a multi-discount purchase is to work through it one step at a time rather than trying to combine the percentages mentally. Enter the original price and the first discount into the discount calculator, then take that result and run it through a second time with the next discount rate, matching the order the store actually applied them in.

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