Formula
ROAS = ad-attributed sales ÷ ad spend
ROAS = 100 ÷ ACoS expressed as a percentage
Worked example
Spend $10 on ads and record $40 in attributed sales: ROAS is 4.0× and ACoS is 25%. Those are two ways to express the same relationship. A 2.0× ROAS corresponds to 50% ACoS; a 5.0× ROAS corresponds to 20% ACoS.
Using Lesson 1’s $40 product with $10 in fees and $14 in landed cost, contribution before ads is $16. At 4.0× ROAS, the $10 ad cost leaves $6. For the second product with $22 in landed cost, that same ROAS produces a $2 loss. The ratio alone cannot tell the two products apart.
Why it matters for profit
The ROAS needed to break even depends on margin. A product with 40% break-even ACoS needs 2.5× ROAS under that contribution model; a product with 20% break-even ACoS needs 5.0×. Allow for the contribution you want to retain before setting a performance target.
ROAS measures attributed revenue per advertising dollar, not profit per advertising dollar. Use the same sales attribution basis and reporting period for comparisons. When ad spend is zero the ratio is undefined; when spend is positive and attributed sales are zero, ROAS is zero while ACoS has no finite value.
Check it on your numbers
Use Catalog Profit Check.
Related terms
Source: Amazon Ads guidance. Platform rules checked October 30, 2026.