Is ROAS the only metric to consider when evaluating your ad or marketing campaign performance? or is there a bigger truth?

ROAS = Return on Ad Spend = Total Sales Revenue / Total Ad Spend

MER = Marketing Efficiency Ratio = Total Sales Revenue / Total Marketing Spend

ROAS is one of the most commonly mentioned (and often overhyped) terms in ads and marketing performance. It calculates the revenue directly attributed to ad spend.

But what about the revenue generated by people who interacted with ads and later converted through other channels?

Let’s consider scenarios where ads contribute to conversions but aren’t typically attributed to ROAS:

1. A user interacts with an ad on their phone, then later converts organically on a desktop (device change—attribution lost).
2. A user interacts with an ad on their phone/desktop, visits the website, gets help via a chat popup, receives a discount link, and converts.
3. A user interacts with an ad, provides their email/phone number, then drops off. In 1-3 days, they receive a discount link via email/WhatsApp and convert.
4. A user interacts with an ad in one browser (e.g., Chrome) but later returns to the website on a different browser (e.g., Mozilla) and converts.
5. A user sees an ad on Instagram/Facebook, takes time to decide (more than 7 days), then visits the website and converts. Since Instagram/Facebook has a 7-day attribution window, this is considered an organic conversion.
6. A user watches a video ad on YouTube but doesn’t click the ad link. Later, they visit organically and convert.
7. A user sees a display ad on the Google Display Network, doesn’t click, but returns organically and converts.

In all these scenarios, ads play a role in the conversion, but there’s no direct attribution. That’s why MER is a much better metric when evaluating ad performance—it provides a more holistic view.

Does that mean calculating ROAS doesn’t matter?

I’m not saying that. What I’m saying is ROAS is not the only metric to consider. As a marketer, founder, or CXO, it helps to look at MER alongside ROAS.

Google Analytics gives a clearer picture of attribution paths for key events, as long as you’re using UTMs correctly in your marketing campaigns.

After reviewing your ROAS, also consider MER and check Attribution Paths in GA4 to see how ads and marketing activities assist in conversions.

ROAS matters — but MER shows you the whole picture.