Calculate the real ROI of Amazon Ads with fees and FBA included

ACoS (Advertising Cost of Sales) is the percentage of ad spend relative to ad-attributed revenue: ACoS = ad spend ÷ ad revenue × 100. It is the inverse of ROAS expressed as a percentage. An ACoS of 25% equals a ROAS of 4x. To know if it is profitable, compare it to your real gross margin: if your margin is 35% and ACoS is 25%, you have a 10% net profit margin.

TACoS (Total Advertising Cost of Sales) divides ad spend by total product sales (organic + paid). A low TACoS shows that your ads are boosting organic ranking and generating sales without paying for every click. It is the key metric for evaluating Amazon investment long-term: a TACoS of 5–10% with an ACoS of 20–30% means 80–85% of your sales are already organic.

On Amazon you must deduct: referral fee (8–15% depending on category), FBA fees (storage + fulfillment, $2–5 per unit), cost of goods, and ad spend. A product you sell for $30 with an $8 cost may leave only $4–6 of real margin after fees and FBA. This calculator uses your real margin data, which you should calculate already deducting Amazon fees and FBA.

With margins below 20% after fees and FBA, Amazon Ads is very hard to make profitable. Minimum CPCs in competitive categories can be $0.50–1.50, and with conversion rates of 10–15%, the resulting CPA can easily exceed your margin. The strategy is to use ads to improve organic ranking (TACoS) rather than directly profiting from each click.

Take your Amazon selling price and deduct: VAT (if applicable), Amazon referral fee (check your category in Seller Central), FBA or own fulfillment fees, cost of goods (manufacturing + shipping to Amazon). The resulting percentage of the selling price is your real margin. Example: $30 price − $4.50 fee (15%) − $3 FBA − $8 product = $14.50 gross profit = 48% margin.