COS - Cost of sales - Not to be confused with Content Optimization System (also the acronym COS) - Cost of sales was more popular than ROAS but have is now rarely seen and is mostly used in retail companies. The calculation is the direct opposite of ROAS, you divide the cost with the revenue that campaign have generated. - Example: NewShoes.com have run a campaign that had an ad spend of 100$. That campaign generated revenue of 410$. - 100 / 410 = 0,24 - The COS of that campaign is 24%.