Open any campaign in the console and you get a row of numbers: impressions, clicks, spend, sales, orders, ACoS, ROAS, CTR, CPC, conversion rate, and whatever else is in the column settings. Most sellers look at ACoS, maybe spend, and move on. That is not wrong, but it means the other numbers, which explain why ACoS is what it is, go unread.

This guide sorts the metrics into three groups: the ones that drive decisions, the ones that explain them, and the ones that mostly generate anxiety. For each, what it means and what to do when it moves.

The five that drive decisions

ACoS

Advertising cost of sales: spend divided by ad-attributed sales. The efficiency number. A 25 percent ACoS means every dollar of ad-driven sales cost 25 cents in ads.

What to do when it moves: nothing yet. ACoS is the symptom, not the cause. Read it at the keyword and search term level, not the campaign level, and then read conversion rate and CPC to find out which one moved it. What counts as a good ACoS depends on margin and on what the campaign is for.

Conversion rate

Orders divided by clicks. Whether the product page closes the shoppers the ad sends. This is the number that separates an ad problem from a listing problem: if conversion rate is low, more ad spend makes everything worse.

What to do when it moves: if it drops, look at the listing first (price, reviews, images, stock) and at the search terms second (are the clicks still relevant). If it rises, bids on the affected keywords can usually go up.

Click-through rate

Clicks divided by impressions. Whether the ad wins attention in the row. Since a Sponsored Products ad is the listing's image, title, price and rating, CTR is mostly a read on those.

What to do when it moves: if it drops on relevant terms, the listing has lost ground to its neighbors on something visible. If it drops on irrelevant terms, add negatives. Low CTR with high conversion means the page is good and the thumbnail is not.

Spend

How much, and where. The number most sellers only see on the invoice. Spend by campaign, by hour, and by placement is where most of the waste in an account is visible.

What to do when it moves: find out where. A spend increase concentrated in one campaign is a budget or bid change; spread across the account, it is usually seasonality or a competitor. Spend by hour tells you whether the overnight windows are earning their cost.

Cost per click

Spend divided by clicks. What the auction is charging you. CPC rises when competition rises, when relevance falls, or when you bid up.

What to do when it moves: if CPC rose and conversion rate did not, ACoS will rise and the bid should come down or the keyword should be reconsidered. If CPC rose and conversion rate rose with it, the placement improved and it may be worth it.

The ones that explain

Impressions. How often the ad was shown. Low impressions on a keyword mean the bid is losing auctions or the keyword has little volume. Useful for diagnosing why a keyword is quiet, not useful as a goal.

Orders and units. The raw count. Useful alongside conversion rate for seeing whether a change in rate is a real shift or a small-sample wobble.

ROAS. Return on ad spend: sales divided by spend. The inverse of ACoS, favored in some reporting. Same information, different shape. Pick one and stay with it.

Placement breakdown. Spend, clicks and sales by top of search, rest of search, and product pages. Not a single metric but the report that makes CPC and conversion rate make sense, because the three placements behave very differently.

TACoS. Ad spend divided by total sales, including organic. Shows whether ads are lifting the whole product or just substituting for organic sales. ACoS versus TACoS covers when each one answers the question you have.

The ones that mostly generate anxiety

Daily ACoS. One day's ACoS on a campaign with a handful of orders is noise. A single large order or a single empty day swings it wildly. Read ACoS over a week at minimum, two for low-volume campaigns.

Account-level anything. The account ACoS is an average of campaigns doing very different jobs. A launch campaign at 80 percent and a mature one at 15 percent average to something that describes neither. Read by campaign and by purpose.

Unsettled numbers. Amazon keeps attributing orders to clicks for days after the click. Yesterday's ACoS is higher than it will be next week. Comparing a fresh period to a settled one is comparing two different measurement windows.

Impression share. Useful for the largest advertisers in a category and mostly a distraction for everyone else. Chasing impression share raises bids on keywords that may not deserve them.

Reading them together

The habit that makes the metrics useful is reading them in pairs. ACoS with conversion rate: is the problem the ad or the page? CTR with conversion rate: does the thumbnail match the page? Spend with sales by hour: are the overnight hours earning their cost? CPC with placement: is the price rising because the placement improved?

Any one number tells you something moved. The pair tells you why, and the why is what you act on. Budget rules and dayparting act on the spend-by-hour pair in particular, and it is the pair that most accounts have never looked at.

Frequently asked questions

What is the single most important Amazon PPC metric?

There is not one, which is the point. ACoS tells you efficiency, conversion rate tells you whether the page closes, click-through rate tells you whether the ad wins attention, and spend tells you how much of your budget is going where. Any one alone misleads. Read ACoS alongside conversion rate at minimum.

Why does my ACoS change after I pull the report?

Amazon attributes sales to clicks within a lookback window, and orders that come in after the click keep being counted for days. A report pulled the morning after will show a higher ACoS than the same day pulled a week later. Compare periods only after both have had time to settle.

Should I track TACoS or ACoS?

Both, for different questions. ACoS measures the efficiency of ad spend against ad-attributed sales. TACoS measures ad spend against total sales, including organic, which shows whether ads are lifting the whole product. A rising ACoS with a flat TACoS can mean ads are doing their job and organic is growing.

Off Hours acts on the spend-by-hour pair: dayparting and budget rules that stop buying the hours that do not sell. Start a free 14-day trial.