ROAS (Return on Ad Spend)

ROAS (Return on Ad Spend) is the multiple of revenue an advertising spend produced:

ROAS = Ad Sales / Ad Spend

A €100 ad spend that generated €400 in attributed sales has a ROAS of 4.0×. ROAS is the mathematical inverse of ACOS:

ROAS = 1 / ACOS    (e.g. ACOS 25% = ROAS 4.0)
ACOS = 1 / ROAS    (e.g. ROAS 5.0 = ACOS 20%)

Both metrics encode the same information. The choice between them is a cultural convention: Amazon-native teams talk in ACOS; teams that grew up in Google Ads, Meta Ads, or DSP environments talk in ROAS. When a stakeholder asks "what's our ROAS?" and another asks "what's our ACOS?", they're asking the same question through two dialects.

When ROAS is the better framing

Three contexts where the multiple-based framing is clearer:

1. Cross-channel reporting. When Amazon Ads is one channel among Google, Meta, and DSP, every other channel reports ROAS. Forcing Amazon into ROAS makes the cross-channel dashboard internally consistent.
2. Hurdle-rate conversations. A CFO who needs a "minimum return of 3× on every euro of marketing spend" expresses that constraint naturally in ROAS.
3. Premium-margin products. A category where margins permit a 5–10× ROAS (ACOS 10–20%) feels less alarming in ROAS than the equivalent ACOS.

When ACOS is the better framing

Two contexts:

1. Inside Amazon. All native reports default to ACOS. Translating into ROAS for an Amazon-only conversation adds friction.
2. Tight-margin categories. ACOS makes the relationship to product margin obvious: a 28% gross margin means ACOS must stay under 28% on the marginal sale. The ROAS equivalent (3.57×) doesn't carry the same intuitive ceiling.

Attributed ROAS vs. incremental ROAS

A critical distinction the headline number hides:

• Attributed ROAS — sales credited to the ad by Amazon's attribution model. What the console reports.
• Incremental ROAS (iROAS) — sales that would not have happened without the ad. The true causal effect.

Branded-keyword attributed ROAS is typically 60–70% incremental (the shopper was looking for you anyway). Generic-keyword attributed ROAS is typically 85–95% incremental. For incrementality discussions, the attributed number overstates the true causal impact.

ROAS in the bid formula

Translating the standard max-bid formula into ROAS:

Max CPC = ASP × CVR / Target ROAS

Compare with the ACOS version: Max CPC = ASP × CVR × Target ACOS. Either form gives the same answer.

Common mistakes

• Confusing percentage ROAS with multiple ROAS. Some platforms express ROAS as a percentage (400%) instead of a multiple (4.0×). Same number, different dialects.
• Comparing channel ROAS at face value. Amazon ROAS is reported within Amazon's attribution model; Google ROAS within Google's. Not directly comparable without a multi-touch model.
• Using attributed ROAS for incrementality decisions. Attributed is the bidding metric; incremental is the budget-allocation metric.
• Hurdle-rate by ROAS without recomputing as margin shifts. When margin changes (price, fee, COGS), the ROAS target moves.