What is ACOS?
Advertising Cost of Sales — ad spend divided by ad-attributed revenue on Amazon.
ACOS stands for Advertising Cost of Sales, the core Amazon PPC metric that divides your ad spend by the revenue those ads directly generated. The acos meaning is simple once you see the formula: ACOS = ad spend ÷ ad-attributed sales, expressed as a percentage. Spend $200 on Sponsored Products and drive $1,000 in ad-attributed revenue, and your ACOS is 20%. It tells you how much of every advertised dollar you handed back to Amazon to win that sale.
ACOS is the inverse of ROAS (return on ad spend): a 20% ACOS is a 5x ROAS. Lower ACOS means more efficient advertising, but "low" is not automatically "good." The number only becomes meaningful when you weigh it against your product's margin, because ACOS measures ad efficiency, not profit. It's possible to run a low ACOS and still lose money once fees and COGS are accounted for.
The ACOS formula and how to calculate it
The acos formula is ad spend divided by ad-attributed sales, times 100. "Ad-attributed sales" matters: Amazon only counts revenue it can tie to a click on your ad within the attribution window — not your total sales for the product. That distinction is what separates ACOS from TACOS (total advertising cost of sales), which divides the same ad spend by your total revenue including organic orders.
A worked example: in a campaign you spent $150 and Amazon attributed $600 of sales to it. ACOS = 150 ÷ 600 = 25%. If that product carries a 40% gross margin before ads, a 25% ACOS leaves roughly 15 points of margin — profitable. The same 25% ACOS on a 20% margin product loses money. The formula never changes; the verdict depends entirely on the margin you compare it to.
- •ACOS = ad spend ÷ ad-attributed sales × 100
- •ROAS = ad-attributed sales ÷ ad spend (the inverse of ACOS)
- •Break-even ACOS ≈ your gross margin percentage before ad spend
- •TACOS = ad spend ÷ total sales (ads plus organic)
What is a good ACOS on Amazon?
There is no universal good ACOS — it's relative to your break-even point, which is your gross margin before advertising. If your product nets a 35% margin after Amazon fees and COGS but before ads, then any ACOS under 35% on that ad spend is contributing profit, and an ACOS above 35% is buying sales at a loss. That break-even ACOS is the only honest benchmark.
The strategic exception is deliberate: new launches, ranking pushes, and seasonal share-grabs often run high ACOS on purpose to drive velocity and organic rank, accepting near-term ad losses for long-term position. That's a defensible choice only if you're tracking it. The danger is running a "low" ACOS that still loses money because your true margin — landed cost, referral fee, FBA fee, returns — is thinner than you assumed.
Why ACOS needs accurate COGS to mean anything
ACOS is an advertising ratio, not a profit figure, so it's only as trustworthy as the margin you judge it against. To know your real break-even ACOS you need true gross margin: revenue minus landed COGS, referral fees, and FBA fees. Get COGS wrong and you'll either starve profitable campaigns or keep pouring spend into losers while the ACOS dashboard looks fine.
This is where ad metrics meet the books. Accurate landed cost per unit and clean fee accounting from your settlements turn ACOS from a vanity ratio into a real decision tool. BeanHawk keeps COGS and Amazon fees accurate from settlement data, so the break-even ACOS you compare against reflects your actual economics rather than a guess.
Frequently asked questions
- What does ACOS stand for?
- ACOS stands for Advertising Cost of Sales. It's an Amazon advertising metric equal to your ad spend divided by the sales those ads were directly attributed to, shown as a percentage. It measures how efficiently your ad budget converts to advertised revenue.
- How do you calculate ACOS?
- Divide your ad spend by your ad-attributed sales and multiply by 100. For example, $250 of spend that drove $1,000 in ad-attributed sales is a 25% ACOS. Only revenue Amazon ties to an ad click counts — not your total product sales.
- What is a good ACOS on Amazon?
- A good ACOS is one below your break-even point, which roughly equals your gross margin before ad spend. If your product margin before ads is 35%, then an ACOS under 35% is profitable on that spend. There's no fixed "good" number; it depends entirely on your margin.
- What's the difference between ACOS and TACOS?
- ACOS divides ad spend by ad-attributed sales only, measuring campaign-level efficiency. TACOS divides the same ad spend by total sales including organic orders, measuring how much advertising costs your whole business. TACOS is better for tracking overall advertising dependence; ACOS is better for tuning individual campaigns.
- Can a low ACOS still lose money?
- Yes. ACOS only measures ad efficiency, not profit. If your true margin after landed COGS, referral fees, and FBA fees is thinner than your ACOS, you're losing money on those advertised sales even though the ACOS looks low. That's why accurate COGS is essential to interpreting ACOS.
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