Ask three Amazon sellers what “good ACOS” looks like and you’ll likely get three different answers — partly because ACOS, TACoS, and break-even ACOS measure three different things, and partly because most explanations of these metrics don’t show how they relate to each other.
Used in isolation, each metric can be misleading. Used together, they form a fairly complete picture of whether advertising is helping or quietly eroding profit. This article walks through what each one measures, where each one breaks down on its own, and how to read them as a set.
ACOS: Campaign-Level Advertising Efficiency
ACOS (Advertising Cost of Sales) measures ad spend as a percentage of the sales generated by that specific advertising — typically at the campaign or ad group level.
Formula:
ACOS = Ad Spend ÷ Ad-Attributed Sales
If a campaign spends $300 and generates $1,500 in attributed sales, ACOS is 20%.
ACOS answers a narrow but useful question: how efficiently is this specific campaign converting spend into ad-driven revenue? What it does not answer is whether that 20% is actually compatible with the product’s margin — a 20% ACOS can be very profitable on one product and deeply unprofitable on another, depending on what’s left in the margin after Amazon’s other fees.
TACoS: Account or Product-Level Advertising Dependency
TACoS (Total Advertising Cost of Sale) measures ad spend against total sales — both organic and advertising-driven — rather than just ad-attributed sales.
Formula:
TACoS = Total Ad Spend ÷ Total Revenue
If total monthly revenue for a product is $40,000 and total ad spend is $4,800, TACoS is 12%.
TACoS answers a different question than ACOS: how reliant is this product’s overall revenue on advertising? A product with a strong ACOS but a high TACoS is generating most of its sales through ads rather than organic ranking — which matters for understanding whether sales volume would hold up if ad spend were reduced. A declining TACoS over time, with stable or growing revenue, is generally a sign that organic sales are picking up the slack from advertising.
Break-Even ACOS: The Margin-Based Ceiling
Break-even ACOS isn’t an efficiency metric at all — it’s a margin calculation that tells you the maximum ACOS a product can sustain before advertising eliminates profit entirely.
Formula:
Break-Even ACOS = Margin Before Advertising ÷ Selling Price
For a product selling at $32, with $13 of margin remaining after COGS and Amazon fees, break-even ACOS is:
$13 ÷ $32 = 40.6%
This means any ACOS below 40.6% leaves some profit on the table after advertising; any ACOS above it means the product is losing money on every ad-driven sale, regardless of how “good” that ACOS might look in isolation.
Putting All Three Together: A Worked Example
| Metric | Value |
|---|---|
| Selling Price | $32.00 |
| COGS + Amazon Fees | $19.00 |
| Margin Before Advertising | $13.00 |
| Break-Even ACOS | 40.6% |
| Actual Campaign ACOS | 28% |
| Total Revenue (organic + ad) | $24,000/mo |
| Total Ad Spend | $3,360/mo |
| TACoS | 14% |
Here, the 28% ACOS is comfortably under the 40.6% break-even threshold, meaning the advertising itself is profitable. The 14% TACoS shows that ad spend represents a modest share of total revenue relative to overall sales — suggesting a reasonably healthy mix of organic and paid demand rather than heavy ad dependency.
If ACOS climbed to 45% while break-even ACOS stayed at 40.6%, the picture would flip: campaigns would be efficient-looking by some standards but actively unprofitable in practice. This is the exact scenario break-even ACOS exists to catch.
When to Use Which Metric
- Use ACOS when evaluating or optimizing a specific campaign or keyword group — it’s the right tool for day-to-day bid management.
- Use TACoS when evaluating how dependent a product’s overall sales are on advertising, especially when deciding whether to test reducing ad spend.
- Use break-even ACOS before setting any bid strategy at all — it defines the ceiling every campaign decision should be measured against.
None of the three should be used as a standalone success metric. ACOS without break-even ACOS tells you nothing about actual profitability. TACoS without margin context tells you nothing about whether the dependency on ads is sustainable. Break-even ACOS without real campaign data is just a target with nothing to compare against.
Common Mistakes
- Treating a “low” ACOS as automatically profitable without checking it against break-even ACOS.
- Comparing ACOS across products with very different margins, as if the same number means the same thing everywhere.
- Ignoring TACoS and only watching campaign-level ACOS, which can hide a growing dependency on paid traffic.
- Calculating break-even ACOS once at launch and never updating it as fees, COGS, or pricing change.
- Reacting to short-term ACOS spikes without checking whether they’re still under the break-even threshold.
FAQ
What’s a good ACOS?
There’s no universal number — a “good” ACOS is any ACOS below the product’s specific break-even ACOS, which depends on margin, not on industry benchmarks.
Is a lower TACoS always better?
Generally, a lower TACoS suggests stronger organic sales relative to ad spend, but an extremely low TACoS in a competitive category can also mean under-investing in visibility. Context matters more than the number alone.
How often should break-even ACOS be recalculated?
Whenever COGS, Amazon fees, or selling price change — which in practice often means quarterly, or immediately after a known fee update.
Can ACOS be profitable even if it looks high?
Yes, if the product has enough margin before advertising. A 50% ACOS can be profitable on a high-margin product and unprofitable on a thin-margin one — that’s the entire reason break-even ACOS exists as a separate metric.
Conclusion
ACOS, TACoS, and break-even ACOS each answer a different question, and none of them is sufficient on its own. ACOS shows campaign efficiency, TACoS shows advertising dependency, and break-even ACOS shows the margin ceiling that makes the other two numbers meaningful. Sellers who track all three — rather than optimizing for a single advertising metric — are in a much better position to know whether their advertising is actually building profit or simply buying revenue. sellerboard tracks ACOS, TACoS, and margin-based break-even thresholds together at the ASIN level, so the three numbers stay connected instead of living in separate reports.
