Amazon advertising · 2 minute read
We're spending more on Amazon ads but total sales aren't growing. Why?
A good ACOS doesn't prove ads are adding sales. Here is what to check when spend rises and total sales don't, and how to check it in thirty minutes.
By Robert Prime
CEO and co-founder
Reviewed by Atouka Tsochataridis
Growth Director
- Published
- Last reviewed
- Sources
- 3 primary and labelled
Cover designed for Mr. Prime.
The short answer
Key takeaways
- ACOS only looks at sales credited to ads, so it can look fine while total sales stay flat.
- Chart total sales, ad sales and ad spend for 12 weeks, and leave out the last 7 days.
- Without the Featured Offer, Sponsored Products gets 0 impressions, so check Buy Box and stock first.
- Split spend into brand and non-brand, then look at spend by product against margin.
By the numbers
- 12
- Weeks of total sales against spend to chart before you change anything
- 7 days
- How long Amazon credits a Sponsored Products sale after a click, for sellers
- 0
- Impressions a Sponsored Products ad gets without the Featured Offer
From Robert Prime and the Mr. Prime team, who run Amazon advertising for founder-led UK and European brands.
Why doesn’t ACOS answer this?
Amazon defines ACOS as ad spend divided by ad revenue1. It only looks at sales credited to ads. So ACOS can look fine while total sales stay flat. Amazon also says attributed sales may not match your retail reports. For sellers, Sponsored Products credits a sale within 7 days of a click, including other products you sell2.
What could be going on?
| Cause | How to check | What to do |
|---|---|---|
| Money on the wrong products | Spend by product against margin | Back products with the margin and conversion to pay for it |
| Ads aren’t serving on some products | Buy Box and stock on your top ad products | Fix those first. Without the Featured Offer, Sponsored Products gets 0 impressions3 |
| Bidding on words you already rank for, including your brand | Split spend into brand and non-brand. Compare with where you rank without ads | Test moving budget to words and shoppers you don’t already reach |
| The listing doesn’t convert | Conversion, reviews and delivery date on the product page | Fix the page before buying more clicks |
| Reading it too soon | How recent is your date range? | Amazon says a date’s figures stay incomplete until the lookback window ends2. Leave out the last 7 days for seller Sponsored Products |
How do I check in thirty minutes?
- Chart weekly total sales, ad sales and ad spend for 12 weeks. Leave out the last 7 days.
- If spend rose and total sales didn’t, split spend into brand and non-brand.
- List your top 10 products by ad spend with their margin, conversion and Buy Box status.
- Find your break-even. Amazon says ACOS needs to stay below your profit margin to make money1.
How can I tell if the ads add anything?
Our suggestion, not an Amazon rule: reduce spend on a small group of products for two weeks, leave a similar group alone, and compare total sales. Avoid peak weeks. It isn’t perfect, but it tells you more than ACOS.
What we have seen
At least 80 separate companies raised ad costs or results in the 12 months of work we reviewed, prospects as well as clients. How we counted.
- Budget on the wrong products came up repeatedly. The change we saw was moving money from weak products to the ones with margin and stock.
- In a few accounts, ads were taking credit for organic sales. Brand words are a good place to start.
Sources
- What is ACOS?. Amazon Ads. Checked 5 November 2026.
- Ad campaign attribution (US help page). Amazon Ads. Checked 5 November 2026.
- Understand Featured Offer eligibility. Amazon Ads. Checked 5 November 2026.
How this guide was made
Written by Robert Prime and reviewed by Atouka Tsochataridis at Mr. Prime, which runs Amazon accounts for UK brands. We used AI tools to help research and draft it; Robert edited it and takes responsibility for it. Every definition and setting was checked against the Amazon page listed above on 5 November 2026. The attribution page is Amazon’s US help page. Where we give our own practice or opinion, we say so.
Every figure above links to the primary source it came from, and we recheck them when Amazon changes its fees or definitions. Read our editorial standards. Spotted something wrong? Tell us through our contact page and we will correct it and note the change here.
About the author
Robert Prime
Robert has spent more than two decades building, growing and selling online businesses, including an Amazon brand he built and sold for seven figures.
His other exits include Telematics.com, sold to LexisNexis, and Remortgage.com. He co-owned UpDownDesk.com.au, growing it on Shopify alone from £12k to £350k a month before he exited, one of more than six Shopify businesses he has built and sold.
He sets and reviews the strategy for every Mr. Prime client, with the view of an operator who has sat on your side of the table.
Reviewed by
Atouka Tsochataridis
A former officer who overdelivers every time. Runs growth across the client book and is on WhatsApp with clients at all hours.
Your numbers, not ours
See your own break-even, TACoS and profit after ads.
The Profit X-Ray works it out from four monthly figures, or from your Business Report, in your browser.