Advertising Cost of Sale (ACOS) is ad spend divided by the sales those ads produced. A 25% ACOS means you spent $25 on ads for every $100 in attributed sales. The number is easy to read, which is why sellers often compare it with benchmarks. The problem is that a benchmark knows nothing about your costs.
What break-even ACOS means
Break-even ACOS is the ACOS at which an ad-driven sale earns zero profit. Any ACOS below it leaves profit on the sale; any ACOS above it means the ad cost more than the sale earned. It equals your profit margin before advertising.
A worked example
These numbers are illustrative, not client data. Suppose a product sells for $30.00. Landed product cost is $8.00, referral fee is $4.50, fulfillment fee is $5.20 and other variable costs (packaging, storage allocation) are $1.30.
| Line | Amount |
|---|---|
| Selling price | $30.00 |
| Product cost | −$8.00 |
| Referral fee | −$4.50 |
| Fulfillment fee | −$5.20 |
| Other variable costs | −$1.30 |
| Profit before ads | $11.00 |
| Break-even ACOS | 36.7% |
At a 36.7% ACOS, every ad sale breaks even. If you want to keep a 15% net margin on ad-driven sales, your target ACOS is roughly 36.7% − 15% = 21.7%.
Why targets differ per product
- Fees vary by size tier and category, so two products at the same price can have very different margins.
- Launch products may run above break-even for a set period to gather data and sales history. That should be a planned, budgeted decision.
- Mature products with strong organic rank can often run at a lower ACOS.
ACOS versus TACOS
Total Advertising Cost of Sale (TACOS) divides ad spend by total sales, including organic. It shows how dependent the whole product is on advertising. A falling TACOS with stable ACOS usually means organic sales are growing.
Putting it into practice
- Calculate break-even ACOS for every advertised product.
- Decide a target margin per product based on its stage: launch, growth or mature.
- Set bids and campaign structure around those targets, not a single account-wide number.
- Review search terms weekly and recalculate when fees or costs change.
Our PPC break-even calculator does the math for you with transparent formulas. It does not pull any live data; you enter your own numbers.
Frequently asked questions
Is a lower ACOS always better?
Not always. Very low ACOS can mean you are underinvesting and missing profitable sales. The right ACOS depends on margin and goals.
Should I include storage fees in the calculation?
Include any variable cost that scales with units sold. An average storage cost per unit is a reasonable approximation.
