What ROAS actually tells you (and what it hides)

Return on ad spend is the first number most clients ask about, and honestly, it’s the least useful one on its own.

A campaign showing 10x ROAS on a €200 daily budget and a campaign showing 4x ROAS on a €5,000 daily budget are not comparable — but they get compared anyway, every week, in almost every reporting call I sit in on.

Here’s what I actually look at before I say a campaign is “working”:

• Marginal ROAS, not average ROAS — what happens to return when you add the next €500, not what the blended number says today
• Contribution margin, not revenue — a 4x ROAS on a low-margin product can lose money; a 2x ROAS on a high-margin one can print it
• Channel interaction — Meta often gets credit for demand that Google or email actually closed

None of this means ROAS is useless. It means it’s a starting question, not an answer. If a client’s entire reporting relies on one blended number, that’s usually the first thing I fix.