You can run a 12% ACOS and be losing market share while you celebrate it. It is the most common pattern we find when auditing Amazon accounts: the team looks at the advertising dashboard, sees a tidy number, and never notices that organic sales have been sliding for four months. ACOS was never designed to catch that. TACoS is.
What each one measures, and the formula
ACOS (Advertising Cost of Sales) is the percentage of your ad-attributed sales that goes on advertising.
ACOS = ad spend ÷ ad-attributed sales × 100
Spend £200 on campaigns, get £1,000 of attributed sales, and your ACOS is 20%. It is a campaign metric. It tells you whether the traffic you are buying is cheap or expensive.
TACoS (Total Advertising Cost of Sales) takes the same spend and divides it by all your sales: the ones that came from ads, plus the ones that came from organic search, from the buy box with no prior click, from a customer who searched for your brand by name.
TACoS = ad spend ÷ total sales × 100
Same £200 of spend, but if total sales for the month were £4,000, your TACoS is 5%. It is a business metric. It tells you how much of your whole account leans on advertising.
The gap between the two numbers is not an accounting detail. It is the share of your business that does not depend on paying for every click.
| ACOS | TACoS | |
|---|---|---|
| What it measures | Efficiency of a campaign, ad group or keyword | How dependent your business is on advertising |
| Formula | Spend ÷ ad-attributed sales | Spend ÷ total sales (organic + paid) |
| When to use it | Tactical calls: raise or lower bids, pause search terms, split budget between campaigns | Business calls: is this product profitable, is the launch working, should we invest more or less |
| What it hides | Whether organic sales are rising, falling or collapsing. It sees nothing outside the ad | Which specific campaign is burning money. It is an average, and averages hide disasters |
| Where you find it | Advertising console in Seller Central, campaign reports | Not calculated for you. You build it by cross-referencing spend with the business report |
That last row explains why so few people look at it: Amazon hands you ACOS and makes you build TACoS by hand.
Why a low ACOS can sit happily on top of a flat business
Picture a seller who decides to "optimise". Bids come down, anything above a 25% ACOS gets paused, and what survives is the branded campaigns plus the keywords that already converted on their own. Account ACOS drops from 28% to 11%. The monthly report looks superb.
What happened underneath is a different story. The paused campaigns were the ones going after generic terms, the searches from people who do not know the brand yet. Those campaigns fed the organic ranking: more clicks and more conversions on a keyword push your product up the results for that search. Cut them and the signal goes quiet. Three months later the product has slipped down the page, organic sales have shrunk, and the account turns over less money with an enviable ACOS.
The reverse case is just as misleading. An 11% ACOS made up almost entirely of branded campaigns (people searching "your brand + product") means you are paying for clicks you would have had for free. Apparent efficiency, real cannibalisation.
The working rule: ACOS is only readable if you know what kind of traffic sits inside it. Branded, generic, competitor and own-product are four different businesses stuffed into one metric.
When TACoS rises: good news versus alarm
TACoS on its own says nothing. It only makes sense read alongside the direction of your total sales. There are four scenarios and they are worth knowing cold.
TACoS up + total sales up. You are investing to grow and the market is answering. Normal during a launch, when entering a new marketplace, or in the run-up to a heavy promotional period. A high TACoS here is not a problem, it is the entry fee. What you watch is that unit margin still holds and that the spike has an expiry date.
TACoS down + total sales up. The best case there is. Organic sales are growing faster than your spend: the product stands on its own, advertising no longer pushes it, it accompanies it. When we see this combination hold for several months, the product has usually locked in organic position and reviews.
TACoS up + total sales flat or falling. Alarm. You are paying more to sell the same or less. Usual causes: a new competitor undercutting you, buy box lost across part of the catalogue, organic position degraded, or campaigns that have started buying worse traffic. Do not fix it by raising budget. Work out which of the four it is first.
TACoS down + total sales falling. The scenario most often mistaken for a win. Spend was cut, the percentage improved, and revenue sank. Exactly the "optimiser" from the section above.
Separating organic sales from paid sales in the reports
There is no button for it. You work it out by subtraction, and you have to be tidy about it:
- Pull the business report by ASIN (Business Reports → Detail Page Sales and Traffic by Child Item) for the period. That gives you units and total sales per product.
- Pull the campaign report for the exact same period and group spend and attributed sales by ASIN.
- Organic sales = total sales − ad-attributed sales.
- Repeat month by month and keep it in a spreadsheet. A single month tells you nothing; the line is what informs you.
Two warnings. First, attributed sales carry an attribution window (Sponsored Products works in days rather than hours, but confirm the current setting in your console), so the split is never surgical. Second, the same shopper can see the ad, not buy, come back three days later through organic search and buy: that sale may land in the ad column even though you would call it organic. Which is why the trend matters more than the decimal.
What TACoS target to set
It depends on two things: your margin and your stage.
| Situation | Reference TACoS | Logic |
|---|---|---|
| New product launch | High, accepting a controlled loss | You are buying ranking and first reviews. Give it an end date and a budget ceiling |
| Product in growth | Mid, trending downwards | Organic should be taking over month by month |
| Mature, profitable product | Low and stable | Advertising defends position, it does not build it |
| Product on thin margin | Very low, or a rethink | If TACoS eats the margin, the problem is the product or the price, not the campaign |
The specific number comes out of your P&L, not out of an article. The calculation that always works: take your contribution margin per unit after product cost, Amazon referral fee and fulfilment (these vary by category and programme, confirm them in Seller Central) and decide what share of that margin you are willing to reinvest. That is your TACoS ceiling. As a sector reference, mature sellers tend to sit comfortably in single digits while accounts opening up a catalogue accept a good deal more for a few months.
Common mistakes when reading the number
- Looking at account-level TACoS. A catalogue mixes mature products with launches. The average hides both. Calculate it per ASIN or per product family.
- Comparing periods with different seasonality. November against September is not a comparison. Use the same month last year.
- Changing campaigns and price in the same week. Pull both levers at once and you will never know which moved the number.
- Reacting to seven days of data. The effect of advertising on organic takes weeks to show. Decide on 30-day windows at minimum.
- Forgetting returns. A lovely TACoS on gross sales can be dreadful on net sales if a lot of stock comes back.
- Treating it as a KPI to minimise. It is not. A 2% TACoS on a product that could triple is a wasted opportunity, not an achievement.
What to do this week
- Calculate monthly TACoS for your five highest-revenue ASINs across the last six months. A spreadsheet will do.
- For those same ASINs, split organic from paid sales and plot both lines. See which one is holding up which.
- Sort every product into one of the four scenarios (TACoS up/down × sales up/down) and write the matching action beside it. Only the "TACoS up, sales not" group needs urgent intervention.
- Check what share of your spend goes to branded campaigns. Above a third, you have a cannibalisation problem that ACOS is hiding from you.
- Set a TACoS ceiling per product based on your real margin and write it down. Without that number on paper, any budget discussion is just an opinion.