How ACOS is calculated on Amazon
Amazon's formula is ACOS = (ad spend ÷ ad revenue) × 100, where ad revenue means attributed sales, and Amazon uses the metric to judge its pay-per-click Sponsored Products campaigns. In digital marketing terms, it expresses retail ad cost as a share of ad-driven sales.
The denominator holds only attributed sales, so the attribution window decides what counts. For Sponsored Products, Amazon credits sales within 7 days of a click for Seller Central advertisers and 14 days for Vendor Central advertisers. Sponsored Brands and Sponsored Display use 14 days for both, and the last ad clicked gets the credit. A Seller Central Sponsored Products ACOS therefore counts fewer days of sales than a Vendor Central one. IAB/MRC guidelines require networks to disclose these windows, and the Amazon Ads guide covers the ad types involved.
Break-even ACOS and target ACOS
Break-even ACOS equals the product's profit margin before advertising. To keep a profit, Amazon says, ACOS has to stay below the profit margin. A product with a 25% margin breaks even at a 25% ACOS, so a 20% ACOS leaves margin over and a 30% ACOS loses money.
Target ACOS follows the goal. Amazon's guidance is to reach break-even first, then decide whether the campaign should grow sales or build awareness, and it notes that new campaigns tend to run a high ACOS because they are new. Margins differ by product, so run the test per SKU. One campaign-level ACOS blends products that break even at different points, and product margins explains how to find each product's break-even point.
ACOS vs ROAS
ACOS and ROAS measure the same efficiency in two formats, and ROAS equals 100 divided by the ACOS percentage.
| ACOS | ROAS | |
|---|---|---|
| Formula | Ad spend ÷ attributed sales × 100 | Attributed sales ÷ ad spend |
| Format | Percentage | Ratio (2.0, or 2:1) |
| Better when | Lower | Higher |
| Amazon's example: $50 spend, $100 sales | 50% | 2.0 |
| Break-even at a 25% margin | 25% | 4.0 |
| Where it is a headline metric | Amazon Ads guidance for Sponsored Products | Walmart Connect Sponsored Search dashboards |
Use ACOS when you manage against product margin, since its break-even line is the margin itself. Use ROAS when you report across networks whose dashboards show it as a headline metric, such as Walmart Connect's Sponsored Search dashboards. Target ROAS and cross-network comparison live under return on ad spend (ROAS).
TACoS: total advertising cost of sales
TACoS divides ad spend by total sales, ad-attributed plus organic, times 100, so it runs lower than ACOS. Sellers and agencies use it to see whether advertising lifts the whole business.
Read the trend. Rising TACoS means ad spend is growing faster than organic sales. Falling or flat TACoS suggests steady advertised sales with organic sales improving. ACOS and TACoS rising together can make sense during a launch. Falling ACOS with rising TACoS means organic sales are shrinking as a share of revenue. A brand focused on total sales may accept a higher ACOS in the short term to improve TACoS over time, as a Tinuiti analyst suggests.
TACoS shows association, and proving the ads caused organic growth takes an incrementality read against a baseline.
Why it matters for brands and sellers
ACOS maps ad spend straight onto product margin, which makes it the practical profitability guardrail for each SKU. The IAB/MRC guidelines recommend SKU-level reporting because most investment promotes specific SKUs, and Amazon warns that ACOS should not be the sole campaign metric. ACOS also counts attributed sales, which include purchases that would have happened without the ad, so a low ACOS says little about incremental value above that baseline. An agency executive told AdExchanger that optimizing to media-attributed ROAS, the same measure inverted, often fails to lift total sales. Comparing Amazon ACOS with another network's ROAS also needs the conversion above and a shared attribution window.
Sellers on the Amazon retail media network can pair ACOS with an Amazon keyword research tool when choosing terms, and our seller guides cover other networks.
Related terms
- Return on ad spend (ROAS): ACOS inverted, with target ROAS and network comparisons.
- Product margins: the margin that sets break-even ACOS.
- Cost per click (CPC): the cost side of every attributed sale.
- Conversion rate: the share of clicks that become attributed sales.
- Incrementality: the sales the ads actually caused.
Frequently asked questions
What does ACOS stand for on Amazon?
ACOS stands for advertising cost of sales. Amazon uses it to measure Sponsored Products campaigns as ad spend divided by attributed sales, times 100. Spending $50 to bring in $100 of attributed sales is a 50% ACOS, and lower is more efficient.
What is a good ACOS on Amazon?
A good ACOS sits below the product's profit margin before advertising, where the ads pay for themselves. Amazon says there is no definitive number, since it depends on industry, company size, and campaign frequency. A 25% margin breaks even at a 25% ACOS.
Is a high ACOS good or bad?
An ACOS above the product's margin loses money on attributed sales, which is bad for a profit campaign. New campaigns tend to run a high ACOS because they are new, Amazon notes. To judge a high ACOS, also check total advertising cost of sales (TACoS): if it is flat or falling, organic sales are likely improving.
What ROAS is a 25% ACOS?
A 25% ACOS equals a ROAS of 4.0, because ROAS is the inverse of ACOS: divide 100 by the ACOS percentage. At a 25% margin before advertising, both mark break-even. Setting a target ROAS is covered under return on ad spend.
