Ad spend divided by attributed sales, the standard efficiency metric in Amazon Ads and other retail media. ACoS is the inverse of ROAS: a 25 percent ACoS equals a 4x ROAS. Total ACoS (TACoS) divides ad spend by total sales including organic, which shows whether advertising is lifting the whole business or only itself.
Related terms
Cite this entry:
Agency Echelon. "ACoS." Agency Echelon Reference, reviewed September 2026. https://agencyechelon.com/reference/glossary/acos/