Five Amazon PPC metrics decide your bids, and the report you read them in changes on 31 December.

The Amazon PPC metrics that matter are the five that decide a bid: cost per click, conversion rate, sales per click, ACoS against your break-even, and TACoS; everything else in the report explains why those moved. Most pages that rank for Amazon PPC metrics give you a glossary of ten or fifteen terms. This post shows how the five fit together into one number you can act on, how to tell which one broke when ACoS jumps, and what changes on 31 December 2026, when Amazon retires the old ad report pages and the numbers you read start coming from a new report with a different way of counting.

The Amazon PPC metrics that set a bid

Every click you buy has a price and a chance of turning into an order. Three numbers describe that, and they multiply into the fourth:

• Cost per click (CPC): spend ÷ clicks. What one visit costs.
• Conversion rate: orders ÷ clicks. How many visits buy. Our guide to Amazon PPC conversion rate covers which version of this number to trust.
• Sales per click: average order value × conversion rate. What one visit brings in.
• ACoS: spend ÷ ad sales, which is the same as CPC ÷ sales per click.

Take an example product with a $25 average order. It pays $0.80 a click and converts at 10%. Each click brings in $25 × 10% = $2.50 in sales, so ACoS is $0.80 ÷ $2.50 = 32%. If its break-even ACoS is 30%, every sale loses a little money. The highest click price that still breaks even is $2.50 × 30% = $0.75.

That is the fifth metric hiding in the first four: break-even ACoS, your profit before ads divided by price. It is not in any Amazon report, so you have to bring it. Without it, ACoS is a number with no line to compare it to. The break-even ACoS guide shows which costs go into it.

When ACoS jumps, split it before you touch a bid

ACoS going from 25% to 32% tells you something got worse. It doesn't tell you what. Two very different weeks produce the same jump:

• The click got dearer. Conversion rate held at 10%, but CPC rose from $0.625 to $0.80. That is the auction: more competitors, a placement adjustment, or a bidding strategy pushing the bid up. A lower bid fixes it. Our post on when an Amazon PPC bid is too high shows where those extra cents come from.
• The click got worse. CPC held at $0.80, but conversion rate fell from 12.8% to 10%. That is the traffic or the listing: new search terms that don't fit, a competitor's deal, a price change, a weak review. Cutting the bid saves money but fixes nothing. Look at the search terms and the product page first.

Both cases show 32% ACoS on a $25 order. Only CPC and conversion rate, read separately, tell you which lever to pull. Make that split a habit and most "my ACoS is up" weeks take ten minutes, not an afternoon.

One more rule for reading any of these: use days whose attribution window has closed. Sponsored Products sales keep arriving for 7 days after the click, so a fresh ACoS always looks worse than it will end up. Our post on the Amazon ads attribution window walks through the numbers.

The rule: a metric matters if a change in it changes a bid, a budget or a listing. Read ACoS against your own break-even on closed days, split it into cost per click and conversion rate before you act, and check TACoS once a month.

TACoS: the metric that catches what ACoS hides

ACoS only sees ad sales. TACoS is ad spend ÷ total sales, ads and organic together (the ACoS, ROAS and TACoS calculator works out all three). It answers a different question: is the business leaning more on ads over time?

Take an example product over three months. Each month it spends $1,200 on ads and makes $4,000 in ad sales: ACoS stays at 30%. But total sales go from $15,000 to $12,000 to $10,000, so TACoS climbs from 8% to 10% to 12%. The ads look exactly as healthy as before. The organic sales underneath them are shrinking, and the ad report alone would never show it.

A rising TACoS with a flat ACoS points away from the bids: rank, price, reviews, stock. A falling TACoS with a flat ACoS is the good case, organic sales growing on top of the ads. Our post on TACoS vs ACoS goes deeper.

Metrics that explain, but don't decide

• Impressions and click-through rate. They tell you whether shoppers see and pick your ad. A low click-through rate points at the main image, the price shown, the review count or a poorly matched search term. Useful for diagnosis; no bid is set from them.
• ROAS. Ad sales ÷ spend, the inverse of ACoS: 32% ACoS is a ROAS of about 3.1. Pick one and stick with it; our ROAS vs ACoS post explains why they describe the same result.
• Spend. A budget question, not a quality one. High spend at a good ACoS is the goal.

Amazon's ad reports change on 31 December 2026

Here is the part most metric guides miss. On 8 June 2026 Amazon made unified reporting generally available in the Ads Console, under Measurement and Reporting > Reporting. In the same announcement it said it is sunsetting the old Sponsored Ads reports page and the Amazon DSP reports page by 31 December 2026. Unified reporting puts Sponsored Products, Sponsored Brands, Sponsored Display and DSP in one report, and Amazon says it is open to all advertisers worldwide who report through the Ads Console.

Three things in that change touch the metrics above.

• Scheduled reports stop. PPC Land (10 June 2026) reports that scheduled reports on the old pages stop running after 31 December unless you recreate them in the new system. Amazon promised an automated migration tool "soon"; don't plan around it.
• The counting changes. Amazon says unified reporting standardises metrics and attribution "from conversion to traffic based attribution". Parker-Lambert (15 June 2026) warns that your numbers may look different from the old reports, and that the difference isn't a bug. Amazon's announcement doesn't say by how much. So a campaign can show a different ACoS in January without anything changing in the auction.
• History has a limit. Amazon keeps up to 15 months of daily or weekly data and up to 6 years at monthly grain. Comparing Black Friday 2026 with Black Friday 2027 day by day will still work; comparing it with the old reports' numbers won't, because they were counted the other way.

The timing is awkward. The old pages go away a month after Cyber Monday, just when you want to compare your peak with last year's. Rebuild your report now, while you can still run both side by side.

What to do this week

1. Write down break-even ACoS for each advertised product. No report has it, and every other number is read against it.
2. Build one weekly report in unified reporting with spend, clicks, cost per click, orders, sales, conversion rate and ACoS per campaign, or per advertised product if you bid by product.
3. Run it for October next to the old Sponsored Ads report. October's windows have closed. Note the gap per campaign, so a January change in the new numbers isn't read as a change in performance.
4. Recreate every scheduled report before 31 December, including any that feed a spreadsheet, a client report or a tool.
5. Download your Q4 reports from the old pages once the Cyber Monday window has closed, so you keep this year's peak in the counting you know.
6. Each week, when ACoS is over break-even, split it into cost per click and conversion rate before you change a bid. Once a month, check TACoS.

Mirox reads these numbers for you and sets the bids. Every bid change is saved with the numbers behind it and the options it ruled out, and exports as CSV, so the record of why a bid moved doesn't depend on which report page Amazon keeps. The 30-day free trial runs live on up to 50 of your parent ASINs in 1 marketplace, on campaigns Mirox builds for them, so your existing campaigns stay untouched.

Common questions

What are the most important Amazon PPC metrics?

Cost per click, conversion rate, sales per click and ACoS measured against your break-even ACoS, plus TACoS once a month. Impressions and click-through rate explain why those move, but they do not set a bid on their own.

What is the difference between ACoS and TACoS?

ACoS is ad spend divided by ad sales. TACoS is ad spend divided by all sales, ads and organic. ACoS tells you whether the ads pay; TACoS tells you whether the business leans more on ads over time.

What is Amazon Ads unified reporting?

The report builder in the Ads Console under Measurement and Reporting > Reporting. It has been generally available since 8 June 2026 and puts Sponsored Products, Sponsored Brands, Sponsored Display and DSP data in one report.

What happens to my scheduled Amazon ads reports after 31 December 2026?

Amazon is retiring the old Sponsored Ads reports and Amazon DSP reports pages by 31 December 2026. Scheduled reports on those pages stop running unless you recreate them in unified reporting.

The one-line version

Read ACoS against break-even, split it into cost per click and conversion rate before you act, watch TACoS monthly, and rebuild your report in unified reporting before 31 December.

Want to see those metrics inside a real bid decision? Read how transparency works, then see what ACoS means for your margin in what is ACoS.