Your ad console says a campaign ran at 40% ACoS last month. Is that good? Bad? Nobody can tell you from that number alone, because it leaves out the one thing that decides whether an ad made money: how much you actually keep from each sale.
That missing piece is called break-even ACoS. Once you know it for each product, every ad report suddenly makes sense. This guide shows you how to work it out in three steps, with a worked example.
ACoS and break-even ACoS, explained
What ACoS means
ACoS stands for advertising cost of sales. It is the share of your ad-driven sales that you spent on ads to get them.
Amazon's own ACoS guide gives the formula:
ACoS = ad spend / ad-attributed sales x 100Example Say you spent $10 on ads and those ads led to $40 of sales. Your ACoS is 10 / 40 = 25%.
A few terms you will see a lot:
- Ad spend is what you paid Amazon for clicks on your ads.
- Attributed sales are sales Amazon credits to your ad, because the shopper clicked it and then bought within a set window of days.
- Lower ACoS means each dollar of ad spend brought in more sales.
Here is the catch. ACoS is measured against the sale price, the full amount the shopper paid. On Merch on Demand you never receive the full sale price. You receive a royalty, which is what is left after Amazon covers printing, shipping, fees and taxes. So ACoS compares your ad cost to money that is mostly not yours.
Printing, the blank, shipping and handling, Amazon's fee
What is left is yours, and it is also the most an ad sale can cost
What break-even ACoS means
Break-even ACoS is the highest ACoS you can run before an ad sale costs you more than the royalty it earns.
The formula is short:
Break-even ACoS = royalty / sale price x 100Think about what that means. If your royalty is 20% of the sale price, then spending 20% of the sale price on ads uses up the entire royalty. You sold a shirt and made nothing. Spend 15% and you keep a little. Spend 30% and you paid to sell that shirt.
- ACoS below break-even: the ad sale made you money.
- ACoS at break-even: you broke even on that sale.
- ACoS above break-even: the ad sale lost money.
Amazon says the same thing in plainer business terms: to stay profitable, ACoS needs to be below your profit margin. On Merch, your royalty is your profit margin, because you have no inventory or shipping costs of your own.
How to calculate it in three steps
Step 1: Find the real royalty
Open your Merch dashboard and look at what a recent sale of that exact product actually paid you, or use the royalty estimate shown when you set the list price. Use the royalty for that product type, in that marketplace, at that price.
Do not use a number from a blog post or a YouTube video. Amazon changes Merch royalties and costs, and in 2026 it introduced Royalty Groups, which can pay different royalties on the same product depending on how your sales are driven. Seller reports say ad-driven sales can count toward the higher groups, but the rules are Amazon's to set, so check the current details in your Merch dashboard and resources.
Step 2: Find the sale price
Use the price the shopper paid, which is normally your list price. If you changed the price recently, use the price that was live when the sales happened.
Step 3: Divide
Royalty divided by price, times 100. That is your break-even ACoS for that product, in that marketplace, at that price.
Above break-even: each ad sale costs more than it earns.
A worked example
Note These are made-up example numbers to show the math. Your real royalties will differ.
Say you sell one design as a standard t-shirt and a hoodie in the US:
| Product | Sale price | Example royalty | Break-even ACoS |
|---|---|---|---|
| Standard t-shirt | $19.99 | $3.00 | 15.0% |
| Same t-shirt, higher price | $22.99 | $5.40 | 23.5% |
| Pullover hoodie | $36.99 | $7.50 | 20.3% |
Now say your t-shirt ad ran at 25% ACoS last month. At $19.99, that ad lost money on every sale: you spent about $5.00 in ads to earn a $3.00 royalty. At $22.99, the same 25% ACoS would be close to break-even.
Same design, same ad, same ACoS, and a completely different result. That is why one "good ACoS" number does not exist.
Why break-even differs per product, marketplace and price
Three things move your break-even ACoS, and on Merch all three change a lot.
Product type
Each product type has its own production cost. A hoodie costs more to print and ship than a t-shirt, a tote bag or a phone case costs something else again. Higher costs eat more of the price, so the royalty share changes from one product type to the next.
Marketplace
The same shirt sold on Amazon.com, Amazon.co.uk and Amazon.de carries different costs, different taxes and a different currency. Prices in Europe include VAT, which takes a slice before any royalty is paid. So a design can have a healthy break-even in one marketplace and a thin one in another.
Price
This is the one people underestimate. Amazon's costs for a product stay roughly the same whether you charge a little more or a little less. So when you raise the price, most of the extra money lands in your royalty (after percentage-based fees and taxes take their share), and your break-even ACoS rises.
Watch out That works in reverse too. Dropping a shirt to the lowest allowed price can leave a royalty so small that almost no ad can be profitable.
Break-even per click, not just per sale
ACoS tells you the result after the fact. To set a sensible bid before you have data, you can turn break-even into a maximum cost per click:
Max cost per click = royalty x conversion rateConversion rate is the share of clicks that turn into an order. Say your royalty is $5.00 and roughly 1 in 10 clicks buys (10%). Then you can afford about $0.50 per click before the ads cost more than they earn. Pay $0.70 per click and you lose money even if the product sells well.
Conversion rates vary a lot from design to design, so use your own numbers once you have a few weeks of data.
Lower the bid by about 43%, then give it a week or two of clicks.
Common mistakes to avoid
- Using one target ACoS for everything. A 25% target might be fine for a well-priced hoodie and a money pit for a cheap shirt.
- Forgetting returns. If a sale is returned, the royalty goes away, but the ad spend does not. A product with lots of returns has a lower real break-even.
- Judging too early. Sales can show up days after the click, so a campaign that looks terrible today can look fine next week.
- Treating break-even as the goal. Break-even means you earned nothing on ad sales. It is a ceiling, not a target. Most sellers aim below it, and only run at or above it on purpose, for example to push a new design or because ad sales may help their Royalty Group.
If you are new to Merch and want the basics first, start with what Merch on Demand is.
How MerchPPC helps
Amazon's ad console knows what you spent, but not what you earn, so it cannot show break-even ACoS. MerchPPC reads your real royalties and your ad data in your own browser and puts break-even ACoS next to each product's ACoS, on the Advertising page. The Catalog then lets you filter for the products that are losing money on ads.
The short version
- ACoS = ad spend / ad-attributed sales.
- Break-even ACoS = royalty / sale price. Above it, the ad sale lost money.
- It changes with product type, marketplace and price, so work it out per product.
- Use your real royalty from the Merch dashboard, since Amazon changes royalties and costs.
- Aim below break-even. For bids, max cost per click = royalty x conversion rate.
Amazon changes its rules, prices and tools from time to time. Check the current details in your Merch and Amazon Ads accounts.