ACoS Calculator
Enter your ad spend and ad sales — get your ACoS and ROAS instantly. This is the first number I check on any Amazon account.
The formula, and what it actually tells you
ACoS (Advertising Cost of Sales) = ad spend ÷ ad sales × 100. It answers one question: how much of every ad-attributed dollar you gave back to Amazon to win it. A 25% ACoS means $0.25 of ad cost per $1.00 of ad sales.
On its own, ACoS is meaningless — 30% is great for a 45%-margin product and fatal for a 20%-margin one. The number that gives it meaning is your break-even ACoS, which is just your pre-ad profit margin. Ads below it make money; ads above it lose money on every click.
How is ACoS calculated?
ACoS (Advertising Cost of Sales) = ad spend ÷ ad sales × 100. If you spent $1,000 on ads to generate $4,000 in ad sales, your ACoS is 25%.
What's the difference between ACoS and ROAS?
They measure the same thing from opposite directions. ROAS = ad sales ÷ ad spend. ACoS = the inverse as a percentage: ROAS of 4× equals an ACoS of 25%.
What is a good ACoS on Amazon?
There's no universal number — it depends entirely on your margins. A good ACoS is one below your break-even ACoS (your profit margin before ad spend). Use the break-even ACoS calculator to find yours.
Should ACoS be as low as possible?
Not always. During launch or ranking pushes, running near break-even buys velocity and organic rank. Once established, hold ACoS at a target set from your margins while scaling spend into what converts.
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