AdvertisingWhat ACOS hides that TACOS shows
ACOS measures ad spend against attributed ad sales. TACOS measures the same spend against total Amazon sales. Read both to understand ad efficiency and business dependence.
ACOS and TACOS use the same numerator and answer different questions.
ACOS = ad spend / ad-attributed sales x 100
TACOS = ad spend / total Amazon sales x 100
Amazon defines ACOS as ad spend divided by attributed ad revenue. Its ACOS guide also notes that there is no universal good percentage.
TACOS widens the denominator to include sales that were not attributed to an ad.
A simple example
During one month, a product has:
- $10,000 in ad spend
- $40,000 in ad-attributed sales
- $100,000 in total Amazon sales
Its ACOS is 25 percent. Its TACOS is 10 percent.
The first number says the campaigns spent 25 cents for every dollar of attributed sales. The second says advertising consumed 10 cents for every dollar of total sales.
Neither number tells you profit. Cost of goods, Amazon fees, promotions, returns, and overhead are still missing.
Where ACOS is useful
ACOS belongs close to the campaign.
Use it to compare targets, search terms, placements, ad groups, and campaigns that share a similar objective. It helps answer whether attributed sales were expensive relative to spend.
Even there, context matters. A branded defense campaign, a product launch, and a mature non-brand campaign may deserve different targets. Attribution windows and campaign type also affect which sales receive credit.
Where TACOS is useful
TACOS belongs close to the product or business.
It helps answer:
- How large is ad spend relative to total sales?
- Is the product becoming more or less dependent on paid support?
- Did total sales grow faster or slower than spend?
- Is a change in campaign efficiency visible in the wider business?
TACOS is especially useful as a trend. A single value has little meaning without margin, lifecycle, and prior periods.
Read the disagreement
| ACOS | TACOS | What may be happening |
|---|---|---|
| Down | Down | Attributed efficiency improved and spend became a smaller share of total sales |
| Down | Up | Campaign efficiency improved, but total sales fell faster or the business became more ad-dependent |
| Up | Down | Attributed sales became more expensive while total sales grew faster than spend |
| Up | Up | Ads became more expensive and consumed a larger share of total sales |
These patterns identify questions. They do not establish causation.
For example, falling TACOS alongside rising total sales is consistent with stronger organic sales. It does not prove that advertising created those sales. Brand demand, distribution, reviews, price, seasonality, or another channel may have contributed.
Use margin to set the boundary
An attractive ACOS can still lose money if the product has thin contribution margin. A high ACOS can be intentional when the goal is a launch, customer acquisition, or inventory reduction.
Write the objective before evaluating the metric:
- Profit: Keep spend within the product's contribution economics
- Growth: Accept a higher cost only with a defined budget and measurement window
- Launch: Separate temporary investment from the mature target
- Defense: Measure the cost of protecting branded demand and question how much would have converted anyway
- Inventory reduction: Judge the campaign beside avoided storage and liquidation costs
One target across every product and lifecycle stage will create bad decisions.
A better monthly read
For each major product, review:
- Total sales
- Ad spend
- Ad-attributed sales
- ACOS
- TACOS
- Contribution margin before and after ads
- Sessions and Unit Session Percentage
Then explain the movement in a sentence:
ACOS improved from 31 to 26 percent, but TACOS rose because total sales declined faster than ad spend. Organic sales and sessions weakened during the same period.
That sentence is more useful than declaring the campaigns healthy because ACOS went down.