Break-Even ROAS & ACoS Calculator

ROAS, return on ad spend, is ad sales divided by ad spend. A ROAS of 3 means every $1 of ads brought in $3 of sales. Break-even ROAS is the ROAS where the ads use up exactly the profit those sales make. Below it, each ad-driven sale loses money. Above it, each one makes money.

Break-even ACoS is the same line seen from Amazon's side. ACoS, advertising cost of sales, is ad spend divided by ad sales, so it's the upside-down version of ROAS. A 25% ACoS is a ROAS of 4. Your break-even ACoS is simply your profit margin before ads: if each sale keeps 40% before ads, you can spend up to 40% of the sale on ads and still break even.

Both numbers come from the same place: what one unit earns after the product, Amazon's fees and getting it to Amazon. That's why this calculator asks for unit costs, not ad results.

profit before ads = price − product cost − FBA fee − referral fee − inbound shipping − other costs
referral fee       = price × referral fee rate
break-even ACoS    = profit before ads ÷ price
break-even ROAS    = 1 ÷ break-even ACoS  (the same as price ÷ profit before ads)
target ACoS        = break-even ACoS − target margin
target ROAS        = 1 ÷ target ACoS

• Price: what the customer pays for one unit, before tax.
• Product cost (COGS): the landed cost of one unit, including packaging and freight to you.
• FBA fee: Amazon's fee to pick, pack and ship the unit. It's in Seller Central under Reports → Fulfillment → Fee Preview.
• Referral fee rate: Amazon's commission for your category. Supplements fall under Beauty, Health and Personal Care: 15% on items over $10 and 8% at $10 or less, applied to the whole price.
• Inbound shipping: the cost to get one unit into Amazon's warehouses, including any inbound placement fee.
• Other costs: storage, returns, prep and anything else you pay per unit.
• Target margin: the share of each sale you want to keep after ads. It's optional.

Take a made-up supplement: a tub that sells for $29.99 on Amazon. These are the example values already in the calculator.

1. Referral fee: $29.99 × 15% = $4.50.
2. All costs per unit: $6.50 product + $4.80 FBA + $4.50 referral + $0.60 inbound + $0.50 other = $16.90.
3. Profit before ads: $29.99 − $16.90 = $13.09.
4. Break-even ACoS: $13.09 ÷ $29.99 = 43.7%.
5. Break-even ROAS: 1 ÷ 43.7% = 2.29.
6. With a 15% target margin: target ACoS = 43.7% − 15% = 28.7%, so target ROAS = 3.49.

So every $1.00 of ads has to bring in $2.29 of sales just to break even, and $3.49 to keep a 15% margin. Notice how much Amazon takes before ads: $9.30 in referral and FBA fees, or 31% of the price.

Lower is better. A low break-even ROAS means a lot of profit per sale, so your ads have more room to work. It depends only on your margin before ads, which is why it varies so much by category, price and fees. Here's how it moves:

Each step down in margin raises the bar faster. At a 20% margin before ads, your ads need a ROAS of 5 just to break even. Low-priced items suffer most, because fixed fees like FBA eat a bigger share of a small price.

A "good" ROAS is therefore not one number. It's any ROAS above your break-even, and above your target ROAS if you want a profit. Those ranges differ by category and margin, so work them out from your own costs, not from someone else's benchmark.

• Leaving out Amazon's fees. Price minus product cost isn't your margin. In the example, fees take 31% of the price before a single ad runs.
• Missing the referral fee threshold. In Beauty, Health and Personal Care, a $10.01 item pays 15% on the whole price, not just the part above $10.
• Mixing up ACoS and TACoS. ACoS divides ad spend by ad sales. TACoS divides it by all sales. Compare your break-even to ACoS or ROAS, not TACoS.
• Judging on the first order only, when customers come back. If people reorder, a first-order ROAS below break-even can still pay off. The sampling ROI and LTV calculator shows how repeat orders change the picture.
• Comparing break-even to a ROAS that isn't real. Reported ROAS counts credit, not cause. More on that below.

Break-even ROAS is the bar. The ROAS you hold up against it has to be the sales your ads actually caused, called incremental sales. Meta's reported ROAS includes people who would have bought anyway. Amazon Attribution misses people who saw an ad and searched Amazon later. Either can put you on the wrong side of the line.

The attribution gap calculator shows how far each report is from what your ads caused. To measure that number, you pause ads in some regions and compare: size the test with the holdout test calculator, then read it with the incremental ROAS calculator. See how lift is calculated for the full method.