ACOS
How much of the revenue your Amazon ads earned went straight back out as Ad Spend.
What it means
ACOS is your Amazon Ad Spend divided by the sales Amazon credits to those ads, expressed as a percentage. Spend €200, earn €1,000 of ad-driven sales, and ACOS is 20% — a fifth of that revenue paid for the advertising. Organic sales sit outside it entirely, so ACOS judges the campaign, not the business.
Show the math
Formula and a worked example
Ad Spend is what Amazon charged you for clicks in the period.
Ad-attributed sales is revenue Amazon credits to those ads, for orders placed inside Amazon's attribution window after a click.
Worked example. A campaign spends €450 in March and Amazon credits it with €1,800 of sales. ACOS = 450 ÷ 1,800 = 25%. A quarter of the revenue those ads produced went straight back to Amazon.
That window is why a paused campaign keeps accruing sales for days after it stops. Wait for the window to close before you judge a change, not the next morning.
It answers the question
Of the money these ads brought in, how much did the ads themselves eat? Below your product margin the campaign makes money; above it, every advertised sale costs you.
Why it matters
ACOS decides whether a campaign stays on. It's the cleanest read you have on whether a campaign buys sales at a price you can live with, because it ignores the organic business running alongside it.
The number it has to beat is your product margin. If 35% of a product's price is gross margin and its ACOS is 40%, every advertised sale of it loses money. That comparison, not the raw ACOS, is the decision.
What good looks like
These bands assume a typical retail margin. The honest threshold is your own: a product with 60% margin carries a much higher ACOS than one at 25%. Read it beside TACOSTACOSHow dependent your whole business is on ads.Under 8% is healthy — ACOS judges the campaign, TACOS judges the business.
How to improve it
| Lever | What you do | Expect | How long | Watch out for |
|---|---|---|---|---|
| Fast Add negative keywords | Pull the search-term report and block terms with clicks but no sales | ACOS down 3–8 points | 1 week | Impressions fall. Block too broadly and you lose discovery on terms that convert slowly. |
| Fast Cut bids on losing keywords | Halve bids where ACOS has run above margin for 14 days straight | ACOS down, spend down | 1–2 weeks | You improved the ratio by shrinking. Total sales usually fall with it — check units, not just ACOS. |
| Slow Fix the listing before the bid | Better main image, clearer bullets, more reviews on the product the ads point at | Same spend converts more | 3–6 weeks | Nothing moves for weeks, and the gain is easy to credit to the wrong change. |
| Slow Raise price or cut unit cost | Widen the margin the ACOS has to fit inside | ACOS unchanged, profit up | 1 quarter | Raising price costs you conversion, so the same clicks buy fewer sales and ACOS gets worse before margin catches up. Cutting unit cost usually means a deeper order and cash locked in stock. |
Every lever costs something somewhere. The last column is the one to read twice.
Read it with
ACOS on its own tells you a campaign's price. Next to spend, it tells you whether to scale it or stop it.
Scaling well
You put more money in and it got cheaper per sale. Rare, and usually means you found headroom in a working campaign.
Buying volume
More spend is producing sales at a worse price. Fine while ACOS sits under your margin — a decision, not yet a problem.
Trimmed the waste
You cut the losing keywords and efficiency improved. Watch that total units held up.
The real alarm
Spending less and paying more per sale. Something changed outside the campaign — Buy Box, price, or a new competitor.
ACOS covers only advertised sales; TACOS covers the whole business. A low ACOS with a rising TACOS means the ads look efficient while the business leans harder on them every month. Neither number shows that alone.
ACOS up with Buy Box % steady is a campaign problem — bids, search terms, or a listing that stopped converting. ACOS up while Buy Box % slips isn't a campaign problem at all: the clicks cost the same and the order goes to another seller. Neither number on its own separates the two.
Common misreads
ACOS only sees advertised sales. A brilliant ACOS on a campaign that touches 3% of your catalogue tells you almost nothing about the business. Read TACOS for that.
Compare it to margin first. An ACOS of 30% on a 55%-margin product still makes money on every sale, and pausing it removes the profit and the organic rank that came with it.
It means no attributed sales yet — impressions with no conversions, or a campaign too new to have any. Read it as no data, not as free sales.
Also called
Advertising Cost of Sales · advertising cost of sale · ad cost ratio
See yoursYour ACOS by campaign and by product, for the last 30 days.
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