Advertising cost of sales, commonly abbreviated as ACOS, measures advertising cost as a percentage of the sales attributed to advertising.
ACOS is widely used when evaluating ecommerce and marketplace advertising, particularly Amazon Ads campaigns. It helps advertisers understand how much they spent on advertising to generate a given amount of attributed sales.
The basic formula is simple, but using ACOS effectively requires more than dividing two numbers. Advertisers must distinguish attributed sales from total sales, calculate a product-specific break-even point, account for margins, and evaluate sales volume alongside advertising efficiency.
Use the OutputMath ACOS Calculator to calculate ACOS, reverse-calculate advertising cost or required revenue, and convert between ACOS and ROAS.
What Is ACOS?
ACOS stands for advertising cost of sales.
The standard formula is:
ACOS = Advertising Cost ÷ Advertising-Attributed Sales × 100
Suppose a campaign spends $1,000 and produces $5,000 in attributed sales:
ACOS = $1,000 ÷ $5,000 × 100
ACOS = 20%
A 20% ACOS means the campaign spent $20 on advertising for every $100 in attributed sales.
ACOS can be calculated at different levels, including:
- Account
- Portfolio
- Campaign
- Ad group
- Advertised product
- Keyword
- Product target
- Search term
- Placement
- Reporting period
Always identify the scope of the calculation. A campaign-level ACOS and an account-level ACOS can describe very different performance.
How to Calculate ACOS
To calculate ACOS:
- Select the campaign, product, target, or reporting period.
- Record the advertising cost for that scope.
- Record the corresponding attributed sales.
- Confirm that both values use the same currency.
- Divide advertising cost by attributed sales.
- Multiply the result by 100.
- Label the result with its scope and reporting period.
Suppose an Amazon Ads campaign reports:
- Advertising cost: $3,600
- Attributed sales: $18,000
Divide advertising cost by attributed sales:
$3,600 ÷ $18,000 = 0.20
Convert the decimal to a percentage:
0.20 × 100 = 20%
The campaign’s ACOS is 20%.
A complete report could state:
The Sponsored Products campaign spent $3,600 and generated $18,000 in attributed sales during the selected reporting period, resulting in a 20% ACOS.
This is more useful than reporting “ACOS: 20%” without identifying the underlying cost, sales, campaign type, or period.
ACOS Formula
The standard ACOS formula is:
ACOS = Ad Spend ÷ Ad-Attributed Sales × 100
Where:
- Ad spend is the advertising cost recorded for the selected campaign or scope.
- Ad-attributed sales is the sales value assigned to that advertising under the platform’s attribution rules.
- Multiplying by 100 converts the result into a percentage.
For example:
- Ad spend: $750
- Attributed sales: $3,000
ACOS = $750 ÷ $3,000 × 100
ACOS = 25%
The campaign spent the equivalent of $25 in advertising for every $100 in attributed sales.
How to Calculate Advertising Cost from ACOS
If attributed sales and ACOS are known, rearrange the formula to calculate advertising cost.
Advertising Cost = Attributed Sales × ACOS ÷ 100
Suppose:
- Attributed sales: $40,000
- ACOS: 15%
The calculation is:
Advertising Cost = $40,000 × 15 ÷ 100
Advertising Cost = $6,000
Advertising cost of $6,000 represents 15% of $40,000 in attributed sales.
This formula can be used to estimate the cost level represented by a target ACOS. It does not guarantee that spending the calculated amount will generate the assumed sales.
How to Calculate Required Sales from Target ACOS
If advertising cost and target ACOS are known, calculate the attributed sales required to reach the target.
Required Sales = Advertising Cost ÷ Target ACOS × 100
Suppose:
- Advertising cost: $5,000
- Target ACOS: 25%
The required sales are:
Required Sales = $5,000 ÷ 25 × 100
Required Sales = $20,000
The campaign must generate $20,000 in attributed sales for $5,000 of advertising cost to represent a 25% ACOS.
Required sales examples
| Advertising cost | Target ACOS | Required attributed sales |
|---|---|---|
| $1,000 | 10% | $10,000 |
| $1,000 | 20% | $5,000 |
| $1,000 | 25% | $4,000 |
| $1,000 | 40% | $2,500 |
| $2,500 | 20% | $12,500 |
| $5,000 | 25% | $20,000 |
A lower target ACOS requires more attributed sales for the same advertising cost.
ACOS Calculation Examples
Sponsored Products example
A Sponsored Products campaign spends $2,400 and generates $12,000 in attributed sales.
ACOS = $2,400 ÷ $12,000 × 100
ACOS = 20%
The campaign spent $20 in advertising for every $100 in attributed sales.
Sponsored Brands example
A Sponsored Brands campaign spends $6,000 and produces $20,000 in attributed sales.
ACOS = $6,000 ÷ $20,000 × 100
ACOS = 30%
Whether this is a good result depends on the campaign objective, attributed-sales definition, product margins, and new-customer value.
ACOS above 100%
A campaign spends $1,500 and generates $1,000 in attributed sales.
ACOS = $1,500 ÷ $1,000 × 100
ACOS = 150%
ACOS can exceed 100%. In this example, advertising cost is greater than the attributed sales value.
Zero advertising sales
If a campaign has advertising cost but no attributed sales, the mathematical calculation requires division by zero.
ACOS is therefore undefined rather than a finite percentage. Some reporting systems may display a blank value, dash, or another placeholder.
Zero advertising cost
If attributed sales are greater than zero and advertising cost is zero:
ACOS = $0 ÷ Attributed Sales × 100
ACOS = 0%
Before accepting the result, confirm that advertising cost has finished reporting and that the attributed sales belong to the selected scope.
ACOS and ROAS Measure the Same Relationship
ACOS and return on ad spend use the same two values in reverse order.
The ACOS formula is:
ACOS = Advertising Cost ÷ Attributed Sales × 100
The ROAS formula is:
ROAS = Attributed Sales ÷ Advertising Cost × 100
As ACOS decreases, ROAS increases.
| ACOS | ROAS percentage | ROAS multiple |
|---|---|---|
| 10% | 1,000% | 10.00x |
| 15% | 666.67% | 6.67x |
| 20% | 500% | 5.00x |
| 25% | 400% | 4.00x |
| 30% | 333.33% | 3.33x |
| 40% | 250% | 2.50x |
| 50% | 200% | 2.00x |
| 75% | 133.33% | 1.33x |
| 100% | 100% | 1.00x |
To convert ACOS into a ROAS percentage:
ROAS Percentage = 10,000 ÷ ACOS Percentage
For a 20% ACOS:
ROAS = 10,000 ÷ 20
ROAS = 500%
To convert ROAS into ACOS:
ACOS Percentage = 10,000 ÷ ROAS Percentage
For a 400% ROAS:
ACOS = 10,000 ÷ 400
ACOS = 25%
Learn more in the ROAS formula guide or use the ROAS Calculator.
What Is Break-Even ACOS?
Break-even ACOS is the advertising cost percentage at which the contribution available before advertising is fully consumed by advertising cost.
Under a simplified product-level model:
Break-Even ACOS = Contribution Margin Before Advertising
Suppose a product sells for $100 and has:
- Product cost: $35
- Marketplace fees: $15
- Fulfillment: $10
- Shipping subsidy: $5
- Other variable costs: $5
The variable costs before advertising are:
$35 + $15 + $10 + $5 + $5 = $70
The contribution before advertising is:
$100 − $70 = $30
The contribution margin is:
$30 ÷ $100 × 100 = 30%
The simplified break-even ACOS is therefore 30%.
At a 30% ACOS, advertising costs $30 for every $100 in attributed sales. This consumes the entire $30 contribution available before advertising.
Under these assumptions:
- ACOS below 30% may leave a positive contribution after advertising.
- ACOS equal to 30% reaches the simplified break-even point.
- ACOS above 30% exceeds the available contribution.
This simplified model does not automatically include fixed overhead, taxes, delayed costs, or repeat-customer value.
Break-Even ACOS Example by Product
Consider three products with different economics.
| Product | Selling price | Contribution before ads | Contribution margin | Break-even ACOS |
|---|---|---|---|---|
| Product A | $50 | $10 | 20% | 20% |
| Product B | $80 | $24 | 30% | 30% |
| Product C | $120 | $60 | 50% | 50% |
A single account-level target of 25% affects the products differently.
- Product A would exceed its simplified break-even ACOS.
- Product B would retain approximately five percentage points of contribution.
- Product C would retain approximately 25 percentage points of contribution.
This is why product economics should be considered before applying one ACOS target across an entire catalog.
How to Calculate Target ACOS
Break-even ACOS describes a boundary. Target ACOS normally needs to reflect the amount of contribution the business wants to retain after advertising.
A simplified formula is:
Target ACOS = Contribution Margin Before Advertising − Desired Post-Ad Contribution Margin
Suppose:
- Contribution margin before advertising: 40%
- Desired contribution after advertising: 15%
The target ACOS is:
Target ACOS = 40% − 15%
Target ACOS = 25%
At a 25% ACOS, $25 of every $100 in attributed sales is used for advertising, leaving $15 from the original $40 contribution under the simplified assumptions.
Target ACOS example
A product sells for $60.
Its costs before advertising are:
- Product cost: $20
- Marketplace fees: $9
- Fulfillment and shipping: $7
- Other variable costs: $3
Total costs before advertising:
$20 + $9 + $7 + $3 = $39
Contribution before advertising:
$60 − $39 = $21
Contribution margin:
$21 ÷ $60 × 100 = 35%
If the business wants to retain a 10% contribution after advertising:
Target ACOS = 35% − 10%
Target ACOS = 25%
This target is based on the product’s economics rather than a generic industry benchmark.
Gross Margin Is Not Always the Same as Contribution Margin
A common mistake is using gross margin as break-even ACOS without checking which expenses have been deducted.
Gross margin may subtract only the product’s direct cost. Contribution margin may also subtract marketplace fees, payment processing, fulfillment, shipping subsidies, packaging, returns, and other variable costs.
Suppose a product has:
- Selling price: $100
- Product cost: $40
- Marketplace and payment fees: $15
- Fulfillment and shipping: $10
Gross margin based only on product cost is:
($100 − $40) ÷ $100 × 100 = 60%
Contribution margin after the listed variable expenses is:
($100 − $40 − $15 − $10) ÷ $100 × 100 = 35%
Using 60% as break-even ACOS would significantly overstate the amount available for advertising under this example.
Define the margin carefully before using it as an advertising threshold.
Product-Level ACOS vs. Campaign-Level ACOS
Campaign-level ACOS can hide differences between products.
Suppose a campaign advertises two products:
| Product | Ad spend | Attributed sales | ACOS |
|---|---|---|---|
| Product A | $500 | $5,000 | 10% |
| Product B | $1,500 | $3,000 | 50% |
Combined advertising cost is:
$500 + $1,500 = $2,000
Combined attributed sales are:
$5,000 + $3,000 = $8,000
Combined ACOS is:
$2,000 ÷ $8,000 × 100 = 25%
The campaign-level result appears to be 25%, but Product B has a 50% ACOS.
If Product B has a low contribution margin, its advertising may be unprofitable even though the combined campaign result appears acceptable.
Review both aggregate and product-level results.
Do Not Average ACOS Percentages Directly
A simple average of campaign percentages can produce a misleading result when sales amounts differ.
Consider:
| Campaign | Ad spend | Attributed sales | ACOS |
|---|---|---|---|
| Campaign A | $200 | $2,000 | 10% |
| Campaign B | $4,000 | $10,000 | 40% |
The simple average is:
(10% + 40%) ÷ 2 = 25%
The weighted combined calculation is:
Total Ad Spend = $200 + $4,000 = $4,200
Total Attributed Sales = $2,000 + $10,000 = $12,000
Combined ACOS = $4,200 ÷ $12,000 × 100
Combined ACOS = 35%
The correct combined ACOS is 35%, not 25%.
Add the underlying advertising cost and attributed sales before calculating the aggregate percentage.
What Are Advertising-Attributed Sales?
Advertising-attributed sales are purchases assigned to advertising under a platform’s attribution rules.
The value may depend on:
- Campaign type
- Account type
- Advertised product
- Purchased product
- Attribution window
- Click or view activity
- Order date
- Reporting date
- Customer behavior
- Marketplace rules
Amazon explains that ACOS represents ad spend relative to attributed sales. The sales scope can differ between campaign types. For example, a report may focus on promoted-product sales or include a broader brand-level sales definition.
Because attribution rules vary, attributed sales should not automatically be treated as identical to total product sales or accounting revenue.
Why Attributed Sales May Differ from Retail Reports
Advertising reports and retail reports may show different sales values even when they appear to cover the same dates.
Possible causes include:
- Different attribution windows
- Click dates versus purchase dates
- Time-zone differences
- Canceled orders
- Returned products
- Payment failures
- Different product scopes
- Delayed attribution
- Different customer identifiers
- Campaign-type differences
- Reporting updates
For example, a customer may click an advertisement near the end of one reporting period and purchase during the next period. One report may associate the sale with the click date, while another records it by order date.
Always identify the source and reporting logic behind the sales figure used in ACOS.
ACOS vs. TACOS
TACOS commonly stands for total advertising cost of sales.
A common TACOS formula is:
TACOS = Advertising Cost ÷ Total Sales × 100
ACOS uses advertising-attributed sales:
ACOS = Advertising Cost ÷ Advertising-Attributed Sales × 100
Suppose:
- Advertising cost: $3,000
- Advertising-attributed sales: $12,000
- Total sales: $30,000
ACOS is:
$3,000 ÷ $12,000 × 100 = 25%
TACOS is:
$3,000 ÷ $30,000 × 100 = 10%
ACOS measures the cost efficiency of attributed advertising sales.
TACOS places advertising cost in the context of total sales, including sales not attributed to advertising.
The metrics should be labeled clearly because they use different denominators.
How to Interpret ACOS and TACOS Together
ACOS and TACOS can provide different views of advertising performance.
ACOS stable and TACOS decreasing
This can occur when total sales grow faster than advertising cost while advertising efficiency remains stable.
It may indicate stronger sales outside the attributed advertising channel, but additional data is required before concluding that advertising caused the change.
ACOS decreasing and TACOS stable
Advertising-attributed sales may be becoming more efficient while total sales do not grow proportionally.
Both ACOS and TACOS increasing
Advertising cost may be growing faster than both attributed sales and total sales.
Both ACOS and TACOS decreasing
Advertising efficiency may be improving while advertising cost represents a smaller share of total sales.
These are possible interpretations, not automatic conclusions. Price changes, inventory, seasonality, competition, promotions, and attribution can also affect the metrics.
ACOS vs. CPA
Cost per acquisition measures advertising cost per conversion or order.
CPA = Advertising Cost ÷ Conversions
ACOS measures advertising cost relative to attributed sales.
Suppose:
- Advertising cost: $2,000
- Orders: 100
- Attributed sales: $8,000
CPA is:
$2,000 ÷ 100 = $20
ACOS is:
$2,000 ÷ $8,000 × 100 = 25%
CPA shows that an order cost an average of $20 to acquire.
ACOS shows that advertising cost represented 25% of attributed sales.
Two campaigns can have the same CPA but different ACOS values if their average order values differ.
ACOS vs. Conversion Rate
Conversion rate compares conversions with clicks or other eligible advertising interactions.
A simplified formula is:
Conversion Rate = Orders ÷ Clicks × 100
ACOS uses cost and attributed sales.
A campaign can have a strong conversion rate but high ACOS when:
- Clicks are expensive
- Average order value is low
- Discounts reduce sales value
- Customers purchase lower-priced products
A campaign can have a lower conversion rate but acceptable ACOS when successful orders have high values.
Use the Conversion Rate Calculator to evaluate conversion frequency separately.
How CPC Affects ACOS
For cost-per-click advertising, ACOS is influenced by cost per click, conversion rate, and average attributed order value.
A simplified relationship is:
ACOS = CPC ÷ (Conversion Rate × Average Order Value) × 100
When using this formula, conversion rate must be entered as a decimal.
Suppose:
- CPC: $1.00
- Conversion rate: 10%, or 0.10
- Average attributed order value: $50
ACOS = $1.00 ÷ (0.10 × $50) × 100
ACOS = $1.00 ÷ $5.00 × 100
ACOS = 20%
If CPC rises while conversion rate and order value remain unchanged, ACOS increases.
If conversion rate or average order value rises while CPC remains unchanged, ACOS decreases.
Use the CPC Calculator for cost-per-click calculations.
Why a Lower ACOS Is Not Always Better
A lower ACOS means advertising cost represents a smaller percentage of attributed sales. It does not automatically mean the campaign produces the best overall business result.
Consider two campaigns:
| Campaign | Ad spend | Sales | ACOS | Contribution before ads |
|---|---|---|---|---|
| Campaign A | $200 | $2,000 | 10% | $800 |
| Campaign B | $2,500 | $10,000 | 25% | $4,000 |
If contribution before advertising is 40% of sales:
Campaign A’s estimated contribution after advertising is:
$800 − $200 = $600
Campaign B’s estimated contribution after advertising is:
$4,000 − $2,500 = $1,500
Campaign A has the lower ACOS, but Campaign B produces more contribution after advertising under these assumptions.
Efficiency and scale should be evaluated together.
ACOS for New Products
A newly launched product may temporarily operate at a higher ACOS because:
- Conversion data is limited
- Keywords are still being tested
- Reviews are limited
- Product-page performance is developing
- Brand recognition is low
- Initial visibility is a campaign objective
This does not mean every high-ACOS launch campaign is acceptable.
Set:
- A maximum acceptable loss
- A test budget
- A review period
- Minimum data requirements
- Clear success criteria
- A plan for adjusting targets
Do not continue an unprofitable campaign indefinitely based only on the possibility of future organic sales.
ACOS for Established Products
Established products often have more historical data for:
- Conversion rate
- Average selling price
- Return rate
- Product margin
- Search terms
- Placement performance
- Seasonality
- Repeat purchases
This can support more precise product-specific targets.
However, historical performance does not guarantee future results. Competition, pricing, inventory, reviews, and marketplace conditions can change.
How to Reduce ACOS
ACOS improves when advertising cost decreases relative to attributed sales.
Potential actions include:
Improve targeting relevance
Review keyword, product-targeting, and search-term reports. Reduce exposure to queries that do not match the product or customer intent.
Use negative targeting carefully
Exclude consistently irrelevant or unproductive traffic after collecting enough data.
Avoid blocking relevant discovery terms based on a very small sample.
Adjust bids using sufficient evidence
A high bid may increase CPC and ACOS. A bid that is too low may reduce impressions and sales.
Evaluate cost, clicks, orders, revenue, and conversion delay before changing bids.
Improve the product detail page
Advertising can bring shoppers to a page, but the page must support the purchase decision.
Review:
- Main image
- Supporting images
- Title
- Product information
- Price
- Availability
- Reviews
- Delivery information
- Variation structure
Separate campaign objectives
Do not compare a profit-focused remarketing campaign directly with a product-launch or awareness campaign without acknowledging the different objectives.
Improve average order value
Multipacks, bundles, complementary products, and pricing changes can affect attributed sales per order. Consider margins and customer value rather than increasing order value at any cost.
Protect inventory availability
Advertising a product that is unavailable or frequently loses purchase eligibility can waste traffic and interrupt performance.
Common ACOS Calculation Mistakes
Reversing the formula
Attributed sales divided by advertising cost calculates ROAS, not ACOS.
Using total sales
Advertising cost divided by total sales produces a TACOS-style measurement rather than standard advertising-attributed ACOS.
Treating ACOS as a profit margin
ACOS measures advertising cost relative to attributed sales. It does not deduct all business expenses.
Using gross margin without checking costs
Gross margin may exclude marketplace fees, fulfillment, shipping, returns, and other variable expenses.
Applying one target to every product
Products can have different margins, prices, return rates, and strategic roles.
Averaging percentages
Combine total advertising cost and total attributed sales before calculating aggregate ACOS.
Ignoring attribution delays
Recent campaign data may not yet include all purchases that will eventually be attributed.
Comparing incompatible campaign types
Campaign types may use different attributed-sales scopes.
Mixing currencies
Advertising cost and attributed sales must use the same currency.
Optimizing from insufficient data
One order can create a dramatic ACOS change when click and sales volume are low.
ACOS Reporting Checklist
Before making a decision from ACOS, confirm:
- Advertising cost is complete.
- Attributed sales are defined.
- Cost and sales use the same currency.
- The campaign type is identified.
- The reporting period is identified.
- The attribution window is understood.
- Product margins are current.
- Returns and cancellations are considered.
- ACOS and TACOS are labeled separately.
- Aggregate ACOS is calculated from totals.
- Product-level differences have been reviewed.
- The sample contains enough clicks and orders.
- ACOS is evaluated with sales volume and contribution.
- The calculation can be reproduced.
Frequently Asked Questions
What is the ACOS formula?
The standard formula is:
ACOS = Advertising Cost ÷ Advertising-Attributed Sales × 100
What does a 20% ACOS mean?
A 20% ACOS means $20 was spent on advertising for every $100 in attributed sales.
Is a lower ACOS better?
A lower ACOS indicates greater advertising efficiency relative to attributed sales. However, it may also be associated with lower advertising delivery and lower total sales. Evaluate efficiency and scale together.
What is a good ACOS?
There is no universal good ACOS. The appropriate target depends on product margin, other variable costs, campaign objective, customer value, and required post-ad contribution.
How do I calculate break-even ACOS?
Under a simplified product-level model, break-even ACOS equals the contribution margin available before advertising.
Is gross margin the same as break-even ACOS?
Not always. Gross margin may exclude marketplace fees, fulfillment, payment processing, shipping, returns, and other variable expenses.
What does a 100% ACOS mean?
A 100% ACOS means advertising cost equals attributed sales. Other product and operating costs would normally make this result unprofitable.
Can ACOS exceed 100%?
Yes. ACOS exceeds 100% when advertising cost is greater than attributed sales.
What is the difference between ACOS and TACOS?
ACOS uses advertising-attributed sales. TACOS generally uses total sales.
What ROAS is equivalent to 25% ACOS?
A 25% ACOS is equivalent to 400% or 4.00x ROAS.
How do I calculate required sales?
Use:
Required Sales = Advertising Cost ÷ Target ACOS × 100
How do I combine campaign ACOS values?
Add advertising cost across the campaigns, add attributed sales, and then divide total cost by total sales. Do not calculate a simple average of percentages.
Why does ACOS change after a campaign ends?
Attributed purchases may be recorded after the advertising interaction. Reporting delays, cancellations, returns, and attribution updates can also change the result.
Calculate ACOS
ACOS is most useful when it is evaluated against accurate product economics and a clearly defined campaign objective.
Calculate the product’s contribution margin before advertising, establish a break-even threshold, and select a target that preserves the desired contribution after advertising. Review product-level performance alongside campaign totals, and do not assume that the lowest ACOS produces the best total business result.
Use the OutputMath ACOS Calculator to calculate ACOS, advertising cost, required sales, or the equivalent ROAS directly in your browser.