Stacked Discount Calculator

How it works

Two discounts stacked together do not simply add up, because the second one applies to the already-reduced price. Each discount multiplies what is left after the previous one:

With the defaults, $100 with 20% off is $80.00. Another 10% off that lands at $72.00, which is a 28% total discount, not the 30% you would get by adding the two percentages together.

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A worked example: $100 with 20% then 10% off

A $100 jacket sits in your cart, with a 20% off code and a 10% loyalty reward that stacks on top. It is tempting to add those up and expect 30% off, but discounts apply one after another, not together.

The first 20% takes the price to $80.00. The second 10% comes off that smaller number, not the original, landing you at $72.00. Your total saving is $28.00, an effective 28% rather than the 30% the codes seemed to promise.

The order of the codes does not change the total, but the myth of simple addition costs shoppers all the time. Enter your own price and two discounts to see where stacking actually leaves you.

Stacking discounts the smart way

• Know the effective rate. Two discounts always combine to less than their sum, so 20% and 10% is 28% off, not 30%.
• Order does not matter. You land on the same final price whichever discount applies first, so do not overthink the sequence.
• Read the fine print. Many stores forbid combining a coupon with a sale, so confirm stacking is allowed before you count on it.

Why the discounts fall short of their sum

The reason twenty percent and ten percent do not make thirty is that each discount works on a different, smaller base. The first one comes off the full price, but the second one comes off what is already left after the first, so it is a percentage of less money. Follow it through with $100:

• First cut, full base. Twenty percent off $100 is a $20 reduction, leaving $80.
• Second cut, shrunken base. Ten percent now applies to that $80, not the original $100, so it is only $8, not $10.
• The missing piece. You lose the extra $2 that a flat thirty percent would have taken, landing at $72 for a real twenty-eight percent off.

The gap is small with modest discounts and grows as they get steeper, but the direction never changes: stacked discounts always come to less than their sum.

Boil a stack down to one number

To compare a stacked offer against a single-discount one, turn the stack into its one equivalent percentage. You cannot add the discounts, but you can multiply what each leaves behind. Multiply the remaining fractions, then see how much you kept:

• Keep, do not cut. Twenty percent off keeps eighty percent, or 0.8; ten percent off keeps ninety percent, or 0.9.
• Multiply the leftovers. 0.8 times 0.9 is 0.72, so you pay seventy-two percent of the original.
• Flip to the discount. Paying seventy-two percent means twenty-eight percent off, the single figure the stack is worth.

With that one number you can judge honestly: a twenty-plus-ten stack at twenty-eight percent off beats a flat twenty-five percent coupon but loses to a straight thirty. The calculator shows this effective rate directly, so you can line any stack up against a single offer.

Where you actually meet stacked discounts

Stacked discounts are not just a math curiosity; they turn up constantly once you know the shape. The classic is a coupon applied on top of a sale, but the pattern repeats wherever two reductions meet on the same purchase:

• Coupon on a sale item. An extra fifteen percent off already-reduced clearance, the everyday version most shoppers see.
• Card or member discount plus a promotion. A store card that takes a percentage off, layered onto a seasonal sale.
• Employee or loyalty discount on top of clearance. A standing personal discount stacked onto whatever is already marked down.

In every case the second discount bites into the reduced price, not the original, so the combined deal is a little less generous than adding the signs suggests. Knowing that keeps your expectations, and your budget, accurate before you reach the register.

A worked example: a coupon on a sale

A coat is $200, already marked thirty percent off in a sale, and you also have a fifteen percent member coupon that stacks. The signs seem to promise forty-five percent off, so you might expect to pay $110. Work the stack properly instead.

Thirty percent off $200 leaves $140. The fifteen percent coupon then comes off that $140, not the original $200, so it takes off $21, landing you at $119. That is a real saving of $81, or about forty point five percent, not the forty-five the two numbers implied.

The $9 difference between the expected $110 and the actual $119 is exactly the shortfall that stacking always hides, and it grows with the size of the discounts. None of this makes the deal bad; forty percent off a coat you wanted is a fine outcome. It just means you should trust the multiplied-out figure, not the sum on the signs, when you decide what you are willing to pay.