In programmatic advertising, ACOS (Advertising Cost of Sales) is a metric used to measure Amazon pay-per-click (PPC) advertising campaigns. It compares the amount spent on PPC campaigns to the amount earned and helps determine if your brand generated campaigns that were cost-efficient. Amazon ACOS helps measure the performance of Sponsored Products ads on Amazon.
Amazon ACOS is calculated by dividing ad spend by ad revenue, then converting it to a percentage. For example, if you spent $50 on an ad campaign and earned $100 from it, your Amazon ACOS would be 50%. ACOS = (ad spend ÷ ad revenue) x 100.
Return on ad spend (ROAS) is the inverse of Amazon ACOS: it is calculated by dividing ad revenue by ad spend. In the example above, the ROAS would be 2.