Amazon advertising guide
Amazon break-even ACoS: formula, example, and target
Break-even ACoS tells you how much of an attributed sale could go to advertising before the modeled unit profit reaches zero.
Guidance checked 24 Sep 2026What ACoS measures
Amazon defines advertising cost of sales, or ACoS, as ad spend divided by attributed ad sales, expressed as a percentage. If a campaign spends $20 and attributes $100 in sales, its ACoS is 20%. Return on ad spend, or ROAS, is the inverse: the same result is a 5.0 ROAS.
ACoS describes advertising efficiency. It does not include product cost, Amazon selling fees, fulfillment, inbound shipping, returns, storage, or other operating costs. Those costs determine whether that ACoS is actually profitable for a specific product.
Calculate break-even ACoS from unit economics
First calculate the profit available before advertising. Subtract the referral fee, FBA or merchant-fulfillment cost, product cost, inbound freight, prep, packaging, storage allowance, expected returns, and other per-unit costs from the selling price.
At exactly break-even ACoS, attributed ad spend consumes all modeled pre-ad profit. Amazon’s own guidance says a profitable ACoS generally needs to be below the product’s profit margin.
A worked Amazon FBA example
Suppose a product sells for $30. After referral fees, FBA fulfillment, the product, inbound freight, prep, storage, and returns allowances, it keeps $9 before ads.
A 30% ACoS would spend the entire $9 on advertising and leave approximately zero modeled unit profit. If the seller wants to keep $4.50 per attributed order, only $4.50 remains available for ads, creating a 15% target ACoS.
| Metric | Result | Meaning |
|---|---|---|
| Break-even ACoS | 30% | Estimated zero-profit ceiling |
| Target ACoS | 15% | Leaves the chosen $4.50 unit profit |
| Break-even ROAS | 3.33 | $3.33 attributed revenue per $1 ad spend |
| Target ROAS | 6.67 | $6.67 attributed revenue per $1 ad spend |
Use the calculator instead of a headline margin
- Enter the selling price, packaged dimensions, and shipping weight in the Amazon FBA profit calculator.
- Add product, inbound, prep, packaging, storage, returns, and other per-unit costs.
- Read the calculated break-even ACoS before entering existing ad spend.
- Choose a target profit and keep the operating ACoS below the resulting target ceiling.
- Confirm an important SKU with Amazon’s current fee tools and your campaign report.
Do not use one target across every ASIN. Products with different prices, size tiers, referral rates, costs, and return patterns have different break-even ACoS values.
Break-even ACoS is not always the campaign goal
A launch, ranking, awareness, or customer-acquisition campaign may intentionally operate above immediate unit break-even. That can be a strategic decision, but it should be measured separately from profitable harvesting. Amazon also recommends looking beyond ACoS at metrics such as ROAS, conversion rate, click-through rate, and return on investment.
Questions sellers commonly ask
What is a good Amazon ACoS?
There is no universal percentage. A good result depends on the product’s economics and the campaign objective. For direct unit profitability, the ACoS must remain below the product’s break-even level.
Is break-even ACoS the same as profit margin?
It is closely related, but only when the margin includes every relevant per-unit cost before ads and uses the same sales basis. Missing fulfillment, returns, storage, or freight will overstate the ceiling.
How do ACoS and ROAS relate?
They are inverses. A 25% ACoS equals a 4.0 ROAS; a 20% ACoS equals a 5.0 ROAS.
Should I calculate ACoS from total sales?
Campaign ACoS uses attributed ad sales. Total ACoS, often called TACoS by sellers, compares ad spend with total sales and answers a different question about advertising’s share of the whole business.
Official sources
This is an independent planning guide. Campaign metrics, attribution, fees, and individual account conditions can change; verify decisions using current Amazon reports.