Why ACOS Is the Wrong Metric to Optimize For
Most Amazon brands optimize PPC to ACOS targets and lose money doing it. Here's why ACOS misleads and what to optimize for instead.
Article summary
Most Amazon brands optimize PPC to ACOS targets and lose money doing it. Here's why ACOS misleads and what to optimize for instead.
Key Takeaways
Three months ago a supplements brand fired their agency. The agency had been hitting their 25% ACOS target every single month for two years. The brand's profit on Amazon was down 22% year over year.
About the Author
This is the problem with ACOS. It is the most-watched number in Amazon PPC. It shows up first on every dashboard, first in every report, first in every agency pitch deck. And optimizing to it has cost the brands I've worked with more money than almost anything else I see in the industry.
The argument I'm making
I'm going to make a case in this post that ACOS is the wrong metric to optimize for. Not the wrong metric to track. There's a difference. It's worth knowing. It just should not be what you are optimizing toward, because optimizing to ACOS means optimizing the wrong outcome.
What ACOS actually measures
If you are spending more than $10,000 a month on Amazon PPC and you are judging your account, your agency, or your in-house manager primarily on ACOS, this post is going to push you to reconsider that.
Why account-wide ACOS targets fail
Key Takeaways ACOS measures spend efficiency, not profit. Two campaigns can have the same ACOS and very different margin contributions. Account-wide ACOS targets are a trap. They aggregate campaigns with different jobs into one misleading number. TACOS is better, but still incomplete. It accounts for organic sales but still does not measure what pays your bills. The metric I optimize for instead is contribution margin multiplied by velocity , broken down by campaign type and product lifecycle stage. Optimizing to ACOS rewards short-term efficiency at the expense of ranking, market share, and brand defense.
The TACOS argument
About the Author Miia Prystupa Amazon PPC Consultant & Marketplace Advertising Director 7+ years hands-on experience managing Amazon PPC across EU and US marketplaces Direct experience with Sponsored Products, Sponsored Brands, Sponsored Display, Amazon Marketing Cloud, and DSP Lite Managed and audited multi-million-dollar annual Amazon ad spend portfolios Former in-house Amazon Ads manager, now advising brands and agencies on scalable PPC systems Last updated: May 2026
What I optimize for instead
ACOS measures how much you spent in ads divided by how much revenue those ads produced. It is a ratio. It tells you nothing about your margin, your product velocity, your organic ranking impact, your inventory turn, your brand defense, or your category share.
How to use ACOS by campaign type
When you set a target ACOS and tell your agency or in-house person "hit this number," you are asking them to optimize a ratio. The fastest way to improve a ratio is usually to do less of the thing that produces a worse ratio. On Amazon that means cutting spend on campaigns that are not converting at your target, especially discovery campaigns, branded defense, and new product launches.
When ACOS targeting is fine
The agency hits the ACOS target. The brand loses long-term position. Both are happening in the data the brand is looking at, but only one is what they thought they were measuring.
Frequently Asked Questions
Quick refresher. ACOS is ad spend divided by ad-attributed revenue. If you spend $30 in ads and those ads drive $100 in sales, your ACOS is 30%.