Amazon Ads ACoS and TACoS explained

What is ACoS?

ACoS stands for advertising cost of sales. Amazon's own guide defines it as ad spend divided by ad revenue, times 100. If you spend $50 on ads and Amazon credits those ads with $100 in sales, your ACoS is 50%. Lower means each dollar of ad-driven sales cost you less. You will see ACoS in the reports for Amazon's sponsored ads, such as Sponsored Products and Sponsored Brands campaigns.

ACoS is the flip side of ROAS (return on ad spend). Amazon notes that ROAS is ad revenue divided by ad spend, the inverse of ACoS. A 25% ACoS equals a ROAS of 4. Use whichever your team finds easier, but keep to one, and see our guide to ROAS vs. ROI for why neither is the same as profit.

Finding your break-even ACoS

A "good" ACoS depends entirely on your margins. Amazon puts it simply: to maintain a profit, your ACOS needs to be lower than your profit margin. Here, profit margin means what is left from each sale after product cost, Amazon fees, shipping and returns, but before advertising.

Example: you sell a product for $40. After product cost, referral fees and fulfillment fees, $12 is left. Your margin before ads is 30%, so your break-even ACoS is 30%. At 30% you make nothing on ad-driven sales; at 20% you keep about $4 per sale. Our break-even ROAS guide shows the same math from the ROAS side.

What is TACoS, and why does it matter?

TACoS means total advertising cost of sales. It is not an official Amazon report metric, but sellers widely use it. The formula: total ad spend divided by total Amazon sales (ad-driven plus organic), times 100. If you spend $1,000 on ads and sell $10,000 in total, your TACoS is 10%.

ACoS only looks at sales Amazon credits to ads. TACoS shows how heavy advertising is across the whole business. That matters because ads on Amazon can lift organic sales too: more sales and reviews can improve where a product appears in normal search results. Reading the two together tells a clearer story:

• ACoS steady, TACoS falling: organic sales are growing faster than ad spend. Usually healthy.
• ACoS steady, TACoS rising: you depend more on ads to hold sales. Look at listings, price and reviews.
• ACoS rising, TACoS falling: you may be paying more per ad sale during a launch that is lifting organic sales. Watch it over a few months.
• Both rising: ads are getting more expensive and not growing the business. Time to cut or restructure campaigns.

Why Amazon's ad sales and your totals differ

Amazon credits a sale to an ad if it happens within a set window after a click. According to the analytics firm Intentwise, Seller Central accounts get a 7-day window for Sponsored Products, while vendors and the Sponsored Brands, Sponsored Display and DSP formats use 14 days. A longer window credits more sales to ads, which lowers ACoS without any change in performance. Compare like with like, and recent days will keep filling in.

Competition also shifts the numbers. In its results for the second quarter of 2026, Amazon reported advertising services revenue of $19.8 billion, up 26% from a year earlier excluding currency effects (see the chart). More advertisers bidding for the same shoppers tends to push click costs, and ACoS, upward.

Track both numbers in one place

Each month, record ad spend, ad-attributed sales, total sales and your margin per product. Then work out ACoS, TACoS and break-even ACoS side by side. Read the trend over three months or more, because a single week can swing on one large order. If you also sell on your own site or other channels, put Amazon next to those so you can see the whole budget. Matrix ROI accepts Amazon Ads and Seller Central exports as spreadsheet uploads and places them beside verified sales from Stripe or your store records, which is how the team at Smith App Studio designed it to be used.