Metrics & KPIs
ACoS
By the AdFlint research team · Last reviewed July 2026
Advertising spend divided by attributed sales revenue, expressed as a percentage; the inverse of ROAS, and the standard vocabulary on Amazon.
Lower is better here, the opposite direction from ROAS, which is where most confusion starts when teams report both. Twenty-five percent equals a four-times ROAS. It also says nothing about profitability until you set it against your break-even margin. The usual misreading is reading a falling number as growth, when it often accompanies shrinking volume instead.
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