ACoS

ACoS stands for advertising cost of sales. Amazon's guide gives the formula as ad spend divided by ad revenue, multiplied by 100, so it is expressed as a percentage. Spend $50 to earn $100 in attributed sales and your ACoS is 50 percent. You see it as a column in Amazon Ads campaign reporting for products like Sponsored Products and Sponsored Brands. Other platforms do not use the term. Google Ads and Meta report return on ad spend or cost per result instead, so ACoS is mostly Amazon vocabulary. The column appears for campaign types such as Sponsored Products, where it measures spend against sales from the promoted products, and for Sponsored Brands, where it measures spend against brand sales. Read the definition shown in your own reports before comparing numbers.

ACoS is the mirror image of ROAS. Amazon describes ROAS as ad revenue divided by ad spend and as the inverse of ACoS. In the same example, $50 of spend and $100 of sales give an ACoS of 50 percent and a ROAS of 2. A 25 percent ACoS is a ROAS of 4, and a 10 percent ACoS is a ROAS of 10. The direction flips: for ACoS a lower number is better, for ROAS a higher one is. Mixing the two in one report is a common source of confusion, so label which one a chart shows. Memorize one conversion table: 50 percent ACoS is a ROAS of 2, 25 percent is 4, 20 percent is 5, and 10 percent is 10. A quick lookup stops the two metrics from being mixed up when a report quotes one and a bid rule uses the other.

On its own, ACoS says nothing about profit. Amazon states that to stay profitable, ACoS must be lower than your profit margin, and that there is no definitive number for a good ACoS because the right target depends on industry, company size, and campaign frequency. The margin that matters is the one before ad cost: sale price minus product cost, Amazon fees, and shipping you pay. The ACoS at which you exactly break even equals that margin percentage, which is why break-even ACoS is simply your margin. Use contribution margin per unit, not the headline price. If a product sells for $40, costs $14 to buy, and carries $6 in Amazon fees and shipping, the margin before ads is $20, or 50 percent, so 50 percent is the break-even ACoS for that item.

The usual misreadings: treating a falling ACoS as growth, when it often comes from cutting spend on the broad terms that bring volume. Chasing a very low ACoS on branded searches that would have converted anyway. Comparing ACoS across product lines with different margins, so a 30 percent ACoS looks bad for a 50 percent margin item and is a loss for a 20 percent one. Ignoring that ads may also lift organic rank, which ACoS counts as zero. And mixing campaigns for launch products with mature ones in one average. Remember that organic sales sit outside the number. A launch campaign can raise a listing's rank, and the sales that follow arrive as organic orders that ACoS never credits to the ads, so an elevated launch ACoS is sometimes a deliberate trade.

To use it this week, calculate each product's margin before ads, set a maximum ACoS below it, and sort campaigns by ACoS against that line. Keep campaigns above the line only on purpose, such as a launch where you accept a loss to gain reviews, and write down the end date. Pair ACoS with total sales and total profit, not alone. If ACoS improves while sales and profit both fall, you cut growth and called it efficiency. Write the target next to the campaign name or in a shared sheet. People who inherit the account later then know which campaigns were meant to run above break-even and for how long.