Advertising Cost of Sales (ACoS) is the percentage of Amazon advertising spend for every dollar you gain in revenue from attributed sales of your marketing campaign. It’s a key Amazon marketing metric. To calculate your ACoS, you need to use the following formula: Total Ad Spend/Attributed Sales = ACoS For example, if you spend a total of $100 on advertising for every $400 you make in advertising attributed sales, you’re ACoS would be 25% for the marketing campaign. $100 Ad Spend/$400 Total Sales = 0.25 ACoS