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Amazon glossary

What is ACoS?

ACoS — Advertising Cost of Sales.

· Reviewed

What is ACoS? — Advertising Cost of Sales
ACoS — Advertising Cost of Sales
ACoS (Advertising Cost of Sales) = ad spend ÷ ad revenue × 100. It measures how much you spend on Amazon ads to make one dollar (or dollar) of ad-attributed sales. Lower is more efficient; your break-even ACoS equals your profit margin.

In depth

ACoS is the headline efficiency metric for Amazon Sponsored Products. An ACoS of 25% means you spent $0.25 in ads for every $1.00 of ad-attributed revenue. It only counts sales Amazon attributes to a click — not organic sales the ad helped drive (that is TACoS). Your break-even ACoS is your contribution margin: if you keep 30% after product cost and fees, an ACoS above 30% loses money on that ad sale, below 30% profits. Work out your own number with the break-even ACoS calculator, then see the guide to lowering ACoS for the levers — bids, negatives, placements — that actually move it.

Formula

ACoS % = (Ad Spend ÷ Ad-Attributed Sales) × 100

Worked example

Say your Sponsored Products campaign for a $9.99 kitchen gadget spent $138 in ads last month and drove $459 of ad-attributed revenue. ACoS = $138 ÷ $459 × 100 ≈ 30%. If your contribution margin after Amazon fees, FBA, and COGS is 34%, you kept 34% − 30% = 4% of that revenue as profit — thin, but positive. If the same campaign spent $200 for $459 revenue (ACoS ≈ 43.6%), you would lose about 9.6% on every ad sale.

When to use it

Report ACoS at the campaign, ad group, and search-term level whenever you need to judge paid efficiency in isolation — e.g. weekly bid reviews, negative-keyword harvesting sessions, or when comparing two campaigns targeting the same product. It is the right lens for tactical PPC decisions.

Common mistakes

  • Chasing an industry-average "good" ACoS (like 25%) instead of computing your own break-even ACoS from real margin — a 40% ACoS is fine for a 55%-margin product and a disaster for a 30%-margin one.
  • Optimising to lowest ACoS instead of highest profit — squeezing ACoS from 28% to 18% by killing volume can shrink total profit even though the ratio looks prettier.
  • Comparing this-week ACoS to last-week without correcting for the 48-hour Amazon attribution lag — recent spend is fully counted, but the sales it drove are still landing.

How AIAdKing handles ACoS

AIAdKing moves each bid toward your target ACoS every night — trimming bids on losing search terms, harvesting non-converting terms as negatives, and concentrating spend where it converts — so ACoS falls without you touching Seller Central by hand.

Related terms

TACoS RoAS Negative keywords All terms →

ACoS — quick answers

What is ACoS?
The share of your ad sales eaten by ad spend — lower is better. Judge every campaign against your own break-even ACoS — your contribution margin — never against an industry-average number.

How does AIAdKing handle ACoS?
AIAdKing moves each bid toward your target ACoS every night — trimming bids on losing search terms, harvesting non-converting terms as negatives, and concentrating spend where it converts — so ACoS falls without you touching Seller Central by hand.

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