Article · About a 10 minute read

ROAS vs MER vs Blended CAC: Which Metric Actually Matters

Matt Putra · Eightx Free Beginner

If full incrementality testing is more than your team can run right now, blended metrics are the honest shortcut, and this article lays them out cleanly. Blended CAC (total spend divided by all new customers) and MER (total revenue divided by total spend) cannot be gamed by any single platform, because they count every rupee of spend against every real customer. For a small team building outside the big startup hubs, this is the most practical way to stop the platforms from grading their own homework.

  • Blended CAC counts all spend against all new customers, so no channel gets to claim cheap wins it did not earn.
  • MER gives you the business level truth: is total spend actually turning into total revenue, across paid, organic, email, and referral.
  • Watch both together. A healthy MER can still hide a CAC your unit economics cannot support.
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The question it answers

  1. How do I stop platform-reported conversions from lying to me about what's actually driving sales?

Read with it

  1. This is the piece that names the exact trap you are in: your ad platforms each claim credit for the same sales, so the numbers... Occam's Razor Essay · About a 15 minute read Marketing Analytics: Attribution Is Not Incrementality Avinash Kaushik
  2. Video · Podcast style conversation, roughly 30 to 45 minutes Measuring Top of Funnel and Incrementality Testing with Zach Epstein from Haus Haus (Zach Epstein)
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