ACOS
Advertising Cost of Sales is a metric used primarily on Amazon that measures ad spend as a percentage of attributed sales revenue. The formula is ACOS = Ad Spend / Ad-Attributed Revenue x 100. Lower ACOS indicates more efficient advertising spend. ACOS is the inverse of ROAS: a 20% ACOS equals a 5:1 ROAS. Amazon reports ACOS for Sponsored Products, Sponsored Brands, and Sponsored Display campaigns individually. Breakeven ACOS equals your pre-advertising profit margin, so if a product has a 30% margin, any ACOS below 30% generates profit while ACOS above 30% loses money on each ad-driven sale.
Why It Matters
ACOS is the primary efficiency metric for Amazon sellers, directly determining whether Sponsored Products and Sponsored Brands campaigns are profitable. Managing ACOS relative to profit margins ensures advertising contributes to bottom-line growth rather than eroding it. Experienced sellers set different ACOS targets by campaign goal: aggressive 40-60% ACOS for product launches prioritizing visibility and ranking velocity, 15-25% for steady-state profitable growth, and under 10% for branded keyword defense campaigns that protect against competitor conquesting.
Example
An Amazon seller spends $200 on Sponsored Products ads and generates $1,000 in attributed sales. The ACOS is $200 / $1,000 = 20%. With a 35% profit margin before advertising, the seller nets 15% profit after ad costs on each sale. The seller optimizes by analyzing ACOS at the keyword level: branded keywords run at 5% ACOS, high-converting product keywords at 18% ACOS, and broad category keywords at 45% ACOS. By reducing bids on category keywords and increasing spend on product keywords, they lower blended ACOS from 20% to 15% while maintaining the same revenue volume.
Related Terms
TACoS
Total Advertising Cost of Sales measures ad spend as a percentage of total sales revenue, including both organic and paid sales. The formula is TACoS = Total Ad Spend / Total Revenue (Organic + Paid) x 100. Unlike ACOS which only considers ad-attributed sales, TACoS provides a holistic view of advertising impact on overall business health. It captures the halo effect of advertising on organic rankings, since Amazon's A9 algorithm rewards sales velocity regardless of whether purchases came through ads or organic search. Healthy TACoS benchmarks range from 5-15% for established products and 15-25% during launches.
ROAS
Return on Ad Spend measures the revenue generated for every dollar spent on advertising, calculated as total attributed revenue divided by total ad spend. A ROAS of 4:1 means four dollars in revenue for each dollar of ad spend. It is important to distinguish ROAS from ROI: ROAS only considers ad spend, while ROI factors in all costs including creative production, agency fees, and overhead. Industry benchmarks vary by channel, with Google Search averaging 2:1 to 8:1, Meta averaging 2:1 to 5:1, and display campaigns often falling below 2:1. A profitable ROAS threshold depends on your gross margin.