Stackable Discount Calculator

Stacking multiplies, which helps you.

Stacking multiplies, which helps you. Sequential discounts multiply rather than add, so 20% then 10% then 5% is 31.6% rather than 35%.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Currency

Price

Contribution margin

First discount

Second discount

Third discount

Price after stacking

$39.67

31.6% effective discount

If the discounts were added$37.70

Stacked sequentially$39.67

Difference$1.97

Contribution left$7.19

Stacking multiplies rather than adds, so 20% plus 10% plus 5% is 31.6% rather than 35%. That works in your favour. It is the one place discount arithmetic is kinder than expected.

How the Stackable Discount Calculator works

Sequential discounts multiply rather than add, so 20% then 10% then 5% is 31.6% rather than 35%. That is the one place discount arithmetic is kinder than expected, and it still takes the price below cost more often than anyone intends.

Also known as: combined discount calculator · stacking coupon codes · multiple discounts total · triple discount calculator · single equivalent discount calculator · trade discount series

Stacked discounts do not add

Two 20% discounts applied in sequence give 36% off, not 40%. The second applies to the already reduced price: 0.8 times 0.8 is 0.64.

Three 10% discounts give 27.1%, not 30%. The gap widens as the discounts get larger and as more are stacked.

Which cuts in your favour when the discounts are applied multiplicatively and against you when a system adds them and applies the total. A checkout that computes 20% plus 20% as 40% is giving away four percentage points more than intended on every order, and this is a genuinely common bug.

The order of operations

Where a fixed amount and a percentage stack, the sequence changes the result. £10 off then 20% off a £100 order gives £72. 20% off then £10 off gives £70.

Neither is more correct; what matters is that the rule is decided, implemented consistently, and stated in the terms. Systems that apply discounts in the order the codes were entered produce different totals for the same basket depending on what the customer did first, which is indefensible when a customer notices.

Tax and shipping placement matters too. A discount applied before or after tax gives different totals, and in the UK and EU the discount reduces the taxable amount, so the sequence is not optional. Getting it wrong overstates or understates the VAT due.

Where the floor should be

Stacking without a floor produces orders below cost, and in a large enough campaign somebody will find the combination.

The protection is a minimum realised margin enforced at the basket level: no combination of discounts may take the order below a stated contribution. That is a rule in the checkout rather than in the terms, and it is the only version that actually holds.

Failing that, exclusivity. Most promotions specify that they cannot be combined with other offers, which is simpler to implement and blunter commercially. It prevents the disaster case and it also prevents the loyal customer with a birthday voucher using it in a sale, which costs goodwill.

What stacking is for

Deliberate stacking has real uses. A sale price plus a loyalty discount rewards the customers you most want to keep. A sitewide promotion plus a first-order voucher acquires customers at a known cost.

The value is that each layer targets a different behaviour and the combination is only available to customers exhibiting both. That is precise targeting rather than a blanket discount, and it is worth more per pound given away.

The condition is that the total is controlled. Layered discounts designed to reach a specific maximum, with a floor enforced, are a sophisticated tool. Layered discounts that happen because nobody set the rules are a leak.

Auditing what actually shipped

The way to find stacking problems is to look at realised discount per order rather than at the promotions in isolation.

Pull the distribution of discount percentage across orders for a promotional period. The tail is where the problems are: orders discounted 60% or 70% when the intended maximum was 30%.

In most campaigns of any size that tail exists and nobody has looked. Finding it costs an hour and the fix is usually a single checkout rule. Not looking means the same tail recurs on every campaign, which over a year is a meaningful sum given away to the small number of customers most practised at finding it.

Where to go next

The Stackable Discount question rarely arrives on its own. These are the ones that usually come with it:

Minimum Discount for Profit Calculator — The floor an automated discount must respect.
Promo Code ROI Calculator — Most of the discount goes to people buying anyway.
Percentage Off Calculator — And the volume it needs to break even.
Etsy Fee Calculator — Every Etsy fee on one sale, itemised.

Not financial advice. Marketplace fees change, and they vary by country, plan and seller status. Every rate here is an editable default, not a quoted price, check the platform's current fee schedule before you price a product against it. This is not tax or business advice.

Frequently asked questions

Do stacked discounts add up?

No. Each applies to the price after the previous one, so the combined effect is always less than the sum. Twenty and ten stacked is 28%, not 30%.

Should I allow codes on sale items?

Only with a floor. Discount codes combining with sale prices is the most common way stores unintentionally sell below cost, and it is entirely preventable in the platform settings.

How do I set a floor?

Calculate the price at which contribution reaches zero, then set the platform's minimum above it. Automating that check is worth more than any single promotion.

Does the order matter?

Not for the final price, multiplication is commutative. It matters for how the saving is presented, and customers generally perceive the largest discount applying first as more generous.