If you run Amazon Ads, you know ACoS. It's the first number most brands look at and often the only one they use to judge whether ads are working. But ACoS only tells part of the story, and managing to it alone can lead you to cut the very campaigns that are growing your business.

What ACoS Measures

ACoS, or advertising cost of sales, is your ad spend divided by the sales attributed to your ads. If you spend $1,000 on ads and they drive $4,000 in attributed sales, your ACoS is 25%.

It's a useful efficiency metric. It tells you how much you're paying for each dollar of ad-driven sales. What it doesn't tell you is how ads affect the rest of your business.

Why ACoS Falls Short

On Amazon, ads and organic sales are closely connected. When ads drive sales, those sales help your products rank higher in organic search, and higher organic rankings drive more sales that ads never get credit for.

That means a campaign with a high ACoS might still be doing important work, like building ranking for a new product or winning a competitive category search. Cut it based on ACoS alone, and you may see organic sales slip a few weeks later without realizing why.

TACoS: The Bigger Picture

TACoS, or total advertising cost of sales, divides your ad spend by your total sales, including organic. Using the same example, if you spend $1,000 on ads and your total sales are $20,000, your TACoS is 5%.

TACoS tells you how dependent your business is on advertising. Watching how it moves over time is one of the clearest signals of whether ads are building your brand:

  • TACoS falling while total sales grow: Ads are helping drive organic growth. This is what you want.
  • TACoS rising while total sales stay flat: You're spending more to hold the same ground. It's time to look at your listings, pricing, or ad mix.
  • TACoS rising while total sales grow quickly: This can be fine during a launch or a big sales push, as long as it's intentional and temporary.

What Else We Watch

Beyond ACoS and TACoS, a few other numbers help round out the picture:

  • Organic rank on key search terms: Are your products moving up for the searches that matter most?
  • New-to-brand customers: How many ad-driven purchases come from shoppers who haven't bought from you in the past year?
  • Margin after ad spend: Sales only matter if they're profitable. We look at what's left after ad costs, not just revenue.

Ads Are One Leg of the Stool

We think about Amazon growth as a three-legged stool. Ads are one leg. The other two are creative and promotional deals, and if any one of them is short, the whole thing wobbles.

  • Ads: The right mix of campaign types, targeting, and budget to put your products in front of the right shoppers.
  • Creative: Strong images and video in your ads, and on the pages your ads send shoppers to: your product detail pages and your Brand Store. Great ads can't make up for a product page that doesn't convert.
  • Promotional deals: Coupons and event deals around moments like Prime Day and Prime Big Deal Days give shoppers a reason to buy now, and they give your ads more to work with.

That's another reason ACoS on its own can mislead you. When your creative improves or a deal goes live, ad efficiency changes too, and the full impact shows up in total sales, not just ad-attributed sales. Measure the whole stool, not one leg.

ACoS is still worth tracking. Just don't let it be the only number you manage to.