Quick answer: Amazon ACOS equals ad spend divided by ad-attributed sales. ROAS equals ad-attributed sales divided by ad spend, the inverse of ACOS. TACOS equals ad spend divided by total sales, including organic. Use ACOS or ROAS for advertising efficiency and TACOS for advertising dependence, always alongside contribution margin.
ACOS, TACOS, and ROAS often appear on the same dashboard, but they don't answer the same question. ACOS and ROAS describe attributed advertising efficiency in inverse formats. TACOS compares advertising spend with all sales. None of them tells you net profit by itself.
The formulas
| Metric | Formula | Example with $1,000 spend |
|---|---|---|
| ACOS | Ad spend ÷ ad sales × 100 | $1,000 ÷ $4,000 = 25% |
| ROAS | Ad sales ÷ ad spend | $4,000 ÷ $1,000 = 4.0 |
| TACOS | Ad spend ÷ total sales × 100 | $1,000 ÷ $10,000 = 10% |
A 25% ACOS and a 4.0 ROAS describe the same attributed relationship.
What ACOS tells you
Advertising Cost of Sales measures spend relative to ad-attributed sales. If a campaign spends $200 and Amazon attributes $1,000 in sales, ACOS is 20%. It's useful for campaign comparison, target and search-term decisions, bid analysis, and break-even advertising calculations, but doesn't include organic sales and doesn't subtract product cost, Amazon fees, returns, or overhead. A 15% ACOS can be unprofitable on a product with a 10% pre-ad contribution margin, and a 45% ACOS can be acceptable during a controlled launch with a clear budget, covered further in ACOS is not profit.
What ROAS tells you
Return on Ad Spend expresses the same relationship as a multiple. If $1 in spend produces $5 in attributed sales, ROAS is 5.0 and ACOS is 20%. Use one consistently, and don't celebrate a ROAS increase without checking whether sales volume collapsed. A campaign moving from 3.0 ROAS to 6.0 looks more efficient, but if attributed sales fell from $30,000 to $3,000, the business may not consider the change a success.
What TACOS tells you
Total Advertising Cost of Sales is calculated against all sales, not only ad-attributed sales. Suppose ad spend is $1,000, ad-attributed sales are $4,000, and total sales are $10,000, ACOS is 25% and TACOS is 10%. TACOS is useful for seeing advertising dependence: if total sales grow while ad spend stays controlled, TACOS may fall even if ACOS remains similar, and it can expose a business whose revenue growth is purchased almost entirely through ads. TACOS is widely used by sellers and software providers, but it isn't a standard Amazon Ads term the way ACOS and ROAS are, so define your formula in reports.
Four common patterns
ACOS down, TACOS down. Advertising efficiency improved and ad spend became a smaller share of total sales, often positive if revenue and profit didn't shrink alongside it.
ACOS stable, TACOS down. Ads convert at roughly the same efficiency while total or organic sales grow faster than spend, indicating stronger organic contribution or repeat demand.
ACOS down, TACOS up. Campaigns became more efficient, but the business became more dependent on advertising or total sales weakened. This pattern deserves investigation.
ACOS up, TACOS up. Advertising became less efficient and consumed more of total revenue. Check CPC, conversion, targeting, and Featured Offer changes.
Break-even ACOS and CPC
A practical break-even ACOS starts with contribution before advertising. Example per unit: selling price $40, Amazon fees $12, product and inbound cost $18, expected returns and other variable cost $2, leaving $8 contribution before ads. Break-even ACOS is roughly $8 divided by $40, or 20%. At 20% ACOS, the product roughly uses the pre-ad contribution, so target ACOS should usually sit below break-even when profit is the goal. If the break-even ad cost per order is $8 and ad click-to-order conversion is 10%, break-even CPC is $8 times 10%, or $0.80, a more actionable bid reference than copying a universal ACOS benchmark.
Why TACOS can improve while profit gets worse
A seller reduced advertising on low-margin products and watched TACOS fall from 14% to 9%, reporting a major improvement. But total sales had also fallen, and a larger share of remaining revenue came from products with high return costs, so net profit declined. TACOS correctly described advertising burden. It didn't describe the entire P&L. Always place ACOS and TACOS beside gross margin, return rate, fees, unit volume, and stock position.
Which metric should you use?
Use ACOS when deciding whether a campaign, target, or search term can support its advertising cost. Use ROAS when your team prefers revenue-return multiples or compares Amazon with other advertising channels. Use TACOS when evaluating account or product-level advertising dependence. Use profit when deciding whether the business actually made money, none of the three ad ratios answer that alone.
EcomSanity tracks ASIN-level sales, FBA stock, sales velocity, days of inventory, conversion, and Featured Offer percentage in one place, so a change in ACOS pulled from your advertising console can be checked against whether it came from the campaign or from the retail offer becoming less competitive. For what to do when a campaign stops spending altogether, see Amazon ads out of budget.
Frequently asked questions
Is a lower ACOS always better?
No. Lower ACOS can come from profitable efficiency, but it can also result from cutting traffic and losing sales. Compare ACOS with sales volume, margin, and business objectives before treating a drop as automatically good.
Is a higher ROAS better?
Usually, but not in isolation. A high ROAS on very little spend can contribute less profit than a lower ROAS campaign running at useful scale.
What is a good TACOS on Amazon?
There's no universal good TACOS. It depends on margin, maturity, repeat purchases, organic rank, category, and growth strategy. Compare the product with its own history rather than a borrowed benchmark.