What is ACOS?

The ACOS formula and how to calculate it

The acos formula is ad spend divided by ad-attributed sales, times 100. The definition is fixed and uncontroversial; what trips sellers up is what belongs in the denominator. "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, so the campaign is 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)

How Amazon attribution actually works

ACOS depends entirely on what Amazon decides to count as an ad-attributed sale, so it's worth understanding the mechanics. When a shopper clicks your ad, Amazon opens an attribution window for that shopper and your products. If they buy within that window, the sale is credited to the ad, even if they came back a week later through search. Different ad types use different windows and different crediting rules, and Amazon has changed these over the years, so check the current documentation for your campaign type rather than assuming.

Two consequences follow. First, ACOS is not a same-day metric. A click today can produce an attributed sale days from now, which means the ACOS you see for a recent date range will drift downward as late conversions land. Judging a campaign on yesterday's ACOS is judging it before the votes are counted. Second, attributed sales can include halo effects: for some campaign types, a click on an ad for one product can credit a purchase of a different product in your brand. That flatters ACOS in ways that have nothing to do with the advertised SKU's own performance.

None of this makes ACOS useless. It makes ACOS a directional efficiency signal that you should read over a mature window (many sellers wait until the attribution period has fully closed before optimizing) rather than a precise profit measure. Precision comes from your books, not the ad console.

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.

Set a target ACOS per product, not per account. A blended account-level ACOS averages your hero product's 12% with your dog's 60% and tells you almost nothing actionable. The useful discipline is a simple table: each SKU's gross margin before ads, its break-even ACOS, and the target you've chosen relative to that break-even (below it for harvest products, above it temporarily for launch products, with an end date).

A full worked example, from ACOS to actual profit

Say you sell a kitchen gadget at $30. These numbers are hypothetical, but the structure is exactly what you'd build for your own SKUs. Your landed cost per unit is $9 (factory price plus freight, duty, and inbound shipping). Amazon's referral fee on the sale is a percentage of price, and the FBA fulfillment fee is a fixed amount per unit for your size tier; suppose together they come to $10.50 on this item. Check the current fee schedule for your real products, because these amounts change.

Gross profit before ads is $30 minus $9 minus $10.50, or $10.50 per unit, which is a 35% margin. Your break-even ACOS is therefore 35%. Now run the ads. In a month, the campaign spends $900 and Amazon attributes $3,000 in sales (100 units) to it. ACOS = 900 ÷ 3,000 = 30%. That's below break-even, so the advertised units earned about 5 points of margin, or roughly $1.50 per unit, $150 total on the attributed sales.

Here's the part sellers skip. Suppose 8 of those 100 units come back as returns. Amazon refunds the buyer, claws back most of your sale proceeds, keeps part of its fees depending on the situation, and the ad spend that won those 8 orders is already gone. Your real ad-side profit drops below the tidy $150. Run the same math with a true margin of 28% instead of the assumed 35% (because you forgot inbound freight in landed cost) and the same 30% ACOS campaign is quietly losing money while the dashboard shows green. The ACOS number was never wrong; the margin it was compared to was.

ACOS vs TACOS vs ROAS: which one should you watch?

Use each metric for the job it's built for. ACOS is a campaign tuning tool: it tells you whether a specific keyword, target, or campaign converts spend into attributed revenue efficiently, so it drives bid changes and negative keywords. ROAS is the same information flipped, popular with sellers who also run Google or Meta ads and want one mental model across platforms. Neither says anything about organic sales.

TACOS is the business health metric. Divide total ad spend by total revenue and you learn how dependent the whole business is on paid traffic. A falling TACOS with steady revenue means organic rank is carrying more weight, which is usually the goal of advertising in the first place. A rising TACOS with flat revenue means you're renting sales you used to own. Watch ACOS weekly at the campaign level and TACOS monthly at the product and account level, and let the accounting numbers (actual net margin after all fees) settle any argument between them.

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.

How ad spend and ACOS show up in your books

Advertising cost never appears as a line called ACOS in your accounting. What actually happens: Amazon either deducts ad spend from your settlement payouts or charges the card on file, depending on your setup. Either way, the bookkeeping treatment is the same idea. Ad spend is an operating expense (usually a "Sponsored ads" or "Amazon advertising" account under selling expenses), recorded in the period the ads ran, and kept separate from Amazon's referral and FBA fees so your margin analysis stays clean.

The trap is netting. If your bookkeeper records only the settlement deposit that lands in the bank, the ad spend deducted inside that settlement vanishes into an understated revenue number, and you can't reconcile the P&L to the ad console at all. Good amazon accounting practice is gross recording: book the full sales, then book fees, refunds, and advertising as their own expense lines, so the deposit is just the net of entries you can actually audit.

This is the main thing to check when evaluating amazon accounting software: does it split advertising out of the settlement as its own expense account, or does it lump it into a generic "Amazon fees" bucket? Tools like A2X, Link My Books, and BeanHawk map settlement lines to distinct accounts so ad spend hits an advertising expense in QuickBooks or Xero. If you're setting up quickbooks for amazon sellers yourself, create the advertising expense account before your first settlement import, and confirm the mapping sends Sponsored Products, Sponsored Brands, and any DSP charges there rather than to cost of goods. Once that's in place, your P&L's advertising line divided by revenue gives you a true TACOS straight from the books, which is a better monthly health check than anything in the ad console.

Common ACOS mistakes

Most ACOS damage comes from a handful of repeatable errors rather than bad bidding. The pattern underneath nearly all of them is treating an attribution-based ad ratio as if it were an accounting fact.

• •Judging ACOS before attribution closes: recent windows always look worse than they'll end up, so sellers panic-cut bids on campaigns that were fine
• •Comparing ACOS to a guessed margin: if landed cost omits freight, duty, or inbound fees, your break-even ACOS is fiction
• •Optimizing account-level ACOS: a blended average hides which SKUs make money; set targets per product
• •Ignoring returns: attributed sales count the order, not whether it stayed sold; high-return products need a lower target ACOS
• •Chasing minimum ACOS instead of maximum profit: cutting spend to make ACOS prettier often shrinks total contribution profit and organic rank
• •Confusing ACOS with TACOS in reporting: quoting one when you mean the other leads to wrong conclusions about ad dependence
• •Letting ad spend hide inside net settlement deposits so the books never show what advertising actually cost

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.

How should Amazon ad spend be recorded in bookkeeping?

As its own operating expense line (advertising or selling expense), recorded gross rather than netted into your settlement deposit. Whether Amazon deducts ads from settlements or charges your card, keep the amount separate from referral and FBA fees so you can compute true margin and a books-based TACOS. Netting it into the deposit understates both revenue and expenses.

Does QuickBooks track ACOS for Amazon sellers?

Not directly. QuickBooks records ad spend as an expense but doesn't know about ad-attributed sales, so it can't compute ACOS; that lives in the Amazon ad console. What quickbooks for amazon sellers setups can give you is the more important number: advertising expense as a percentage of total revenue (TACOS) straight from the P&L, provided a connector like A2X, Link My Books, or BeanHawk maps settlement ad charges to a dedicated advertising account.

What tools help manage ACOS and the accounting behind it?

Two different categories. PPC tools (bid optimizers and the ad console itself) manage the ACOS number. Amazon seller accounting software manages whether that ACOS is actually profitable, by keeping landed cost, fees, and returns accurate so your break-even ACOS is real. Most serious FBA sellers end up with one of each; compare amazon fba accounting options on how cleanly they split ad spend and fees out of settlements, since that's the data your ACOS targets depend on.

Related terms

Go deeper

• Amazon PPC for Profit-Minded Sellers: ACOS, TACOS & True Margin
• Amazon Profit Margins: The Real Cost Stack From Sale to Net