What is ACoS on Amazon? The definition, and the number that actually matters.
ACoS is ad spend divided by ad revenue. What counts as a good one depends entirely on your break-even, which most sellers have never actually calculated.
ACoS is Advertising Cost of Sale: the percentage of your ad-driven revenue that you spent on ads.
ACoS = ad spend ÷ ad revenue × 100
Spend $250 on ads, make $1,000 in sales attributed to those ads, and your ACoS is 25%. That is the whole definition. The interesting part is what it does and does not tell you.
What ACoS does not tell you
It is not profit. ACoS ignores your product cost, FBA fees, referral fees, returns and storage. A 25% ACoS on a product with a 20% margin is a loss. A 45% ACoS on a product with a 60% margin is fine. The number is meaningless without your unit economics beside it.
It only counts ad-attributed sales. Organic sales are not in the denominator. This matters more than it sounds: an account can show a rising ACoS while total profit improves, because advertising is lifting organic rank. ACoS cannot see that. TACoS can — more below.
Attribution has a window. Amazon credits a sale to an ad click within a set lookback period. Sales outside that window, or on a different device where the shopper was not recognised, are invisible to ACoS. The number is directionally right and precisely wrong.
The number that actually matters: break-even ACoS
Your break-even ACoS is the point at which an additional advertised sale makes you exactly nothing. It is simply your profit margin before ad spend, expressed as a percentage of price.
Work it out properly:
| Line | Example |
|---|---|
| Selling price | $40.00 |
| Cost of goods | −$12.00 |
| FBA fulfilment fee | −$5.50 |
| Referral fee (15%) | −$6.00 |
| Returns / storage allowance | −$1.50 |
| Profit before ad spend | $15.00 |
| Break-even ACoS | $15.00 ÷ $40.00 = 37.5% |
At 37.5% ACoS this product breaks even on advertised sales. Below that you make money. Above it you are buying revenue at a loss — which is a legitimate choice for a launch, where you are paying for rank and reviews, and a slow bleed everywhere else.
Most sellers have never done this calculation for their actual current costs. Fees change, COGS changes, return rates change. A target ACoS set once, by someone who has since left, against a margin that has since moved, is the most common expensive mistake in Amazon advertising. Run the numbers for your product if you want it done for you.
So what is a good ACoS?
There is not a universal one, and anyone quoting you a benchmark without asking about your margin is guessing. The honest answer:
- Below break-even → profitable on ad-driven sales
- At break-even → buying volume and rank at cost
- Above break-even → deliberate investment, or a leak
Which of those you should target depends on where the product is in its life. Launches often run above break-even on purpose. Mature products generally should not. We go into the benchmark question properly in what counts as a good ACoS.
ACoS vs TACoS vs ROAS
ROAS is simply ACoS inverted — revenue divided by spend, expressed as a multiple. 25% ACoS = 4× ROAS. Same information, different convention. Use whichever your team thinks in; do not let anyone tell you one is more sophisticated. The long version of that argument is here.
TACoS — Total Advertising Cost of Sale — is ad spend divided by total revenue, organic included:
TACoS = ad spend ÷ total revenue × 100
This is the more useful business metric, and the one to watch over months rather than weeks. A TACoS that falls while ad spend holds steady means paid is pulling organic up behind it — advertising is building something. A TACoS that is flat or rising means you are renting the sales. We unpack it in TACoS vs ACoS.
The practical rule: ACoS tells you about the ad. TACoS tells you about the business.
How to actually lower ACoS
In rough order of how much they typically return:
- Add negatives for search terms that spent without converting. Usually the largest single line and the cheapest to fix.
- Bid to your ceiling, not by feel. Target ACoS × average order value × conversion rate gives the maximum rational bid for each keyword. Most accounts have keywords well under it and well over it simultaneously.
- Improve conversion rate. Images, title, bullets, price, reviews. A conversion-rate improvement lowers ACoS on every keyword at once, which no bid change can do.
- Stop advertising out-of-stock ASINs. You lose the spend once, then bid on the poisoned conversion data for weeks afterwards.
- Fix self-competition. The same term winning impressions in two of your campaigns costs you more per click and splits the conversion history so neither campaign learns.
Note that only two of those five are bidding changes. Most ACoS problems are not bid problems — which is why the weekly management checklist spends more time on search terms and structure than on bids.
The check worth running on your own account
Take five keywords at random. For each one, work out the theoretical maximum bid — target ACoS × average order value × conversion rate — and compare it to what you are actually bidding.
If you cannot do that calculation because you do not know the conversion rate, that is the finding. Under about 15 clicks there is no meaningful conversion rate to know, and any bid on that keyword is a guess. Sum the spend across every keyword in that state and you have the share of your budget being bid on nothing.
That number is usually much larger than people expect, and it is the single best argument for treating "0 conversions in 8 clicks" and "0 conversions in 300 clicks" as different evidence — which rules-based tools do not. It is check 3 of the twelve we run on every account.
The one-line version
ACoS is ad spend ÷ ad revenue, it is not profit, and the only number that makes it mean anything is your break-even — your margin before ad spend, recalculated against today’s fees rather than last year’s.
Common questions
- What is ACoS on Amazon?
- ACoS (Advertising Cost of Sale) is ad spend divided by ad-attributed revenue, expressed as a percentage. Spending $250 to generate $1,000 in advertised sales is a 25% ACoS.
- What is a good ACoS on Amazon?
- There is no universal figure — it depends on your margin after COGS, FBA fees, referral fees and returns. The meaningful threshold is your break-even ACoS, which equals your profit margin before ad spend. Below it you profit; above it you are buying revenue at a loss.
- How do you calculate break-even ACoS?
- Subtract cost of goods, FBA fulfilment, referral fee and a returns allowance from the selling price to get profit before ad spend, then divide that by the selling price. A $40 product with $15 profit before ads has a 37.5% break-even ACoS.
- What is the difference between ACoS and TACoS?
- ACoS uses only ad-attributed revenue; TACoS uses total revenue including organic. ACoS tells you how the ad performed, TACoS tells you what advertising is doing for the business. A falling TACoS at steady spend means paid is lifting organic.
- What is the difference between ACoS and ROAS?
- They are inverses of each other. ROAS is revenue divided by ad spend as a multiple; ACoS is ad spend divided by revenue as a percentage. A 25% ACoS is a 4× ROAS. Neither is more accurate.
If you would rather not spend the afternoon: we will run the audit on your account and send you the findings. No card, and you keep the report whether or not you go further.