Step one: gross margin before ad spend
Before calculating any target ACoS, you need to know the product's gross margin without counting ad spend — that is, how much of the selling price is left after subtracting what it costs to get that product into the customer's hands.
| Gross margin (%) | = | (Selling price − COGS − Amazon referral fee − FBA fees − other variable costs) ÷ Selling price × 100 |
That margin is your ad spend "ceiling": if you spend more than that on ads to sell the product, it loses money, no matter how much it sells.
Break-even ACoS
Since ACoS is the ratio of ad spend to attributed sales, break-even ACoS is exactly equal to the gross margin calculated above:
| Break-even ACoS | = | Gross margin (%) before ad spend |
At that ACoS, the product neither makes nor loses money on that sale — the ad spend consumed exactly the margin that would have been left.
Target ACoS: break-even minus your desired profit margin
Break-even ACoS isn't the target — it's the limit. The real target has to leave a profit margin after ad spend:
| Target ACoS | = | Break-even ACoS − Desired profit margin (%) |
If your desired profit margin is, say, 10% of the selling price, your target ACoS is the break-even ACoS minus those 10 percentage points.
Full example
| Item | Value |
|---|---|
| Selling price | $40.00 |
| Product cost (COGS) | $12.00 (30%) |
| Amazon referral fee | $6.00 (15%) |
| FBA fees | $4.80 (12%) |
| Other variable costs (storage, returns, inbound shipping) | $3.20 (8%) |
| Gross margin before ad spend | 35% ($14.00) |
| Break-even ACoS | 35% |
| Desired profit margin | 10% |
| Target ACoS | 25% |
For this product, a campaign running at 25% ACoS leaves 10% net profit on the selling price. The same campaign at 35% ACoS wipes out the profit. And at 40% ACoS, the product is already losing money — even while selling well.
Why a single target for the whole catalog is a mistake
It's common to see generic targets like "keep ACoS under 20%" applied to the whole catalog. The problem: each product has a different gross margin. A product with a 45% margin has room for a break-even ACoS well above 20% — the generic target is leaving ad budget on the table. Meanwhile, a product with a 15% margin is already losing money at 20% ACoS, even though the target "looks good" on paper.
Target ACoS is a property of the product, calculated from its margin — not a number you set once for the whole account.
How EcomVision helps
EcomVision's Net Profit dashboard already calculates each product's real margin — with COGS, Amazon referral fees, FBA fees and other costs factored in automatically. Because those numbers already live in the platform, each product's break-even ACoS is visible without building a spreadsheet, and the Advertising & Growth dashboard shows each campaign's real ACoS side by side with that benchmark.
