Marketing Efficiency Ratio (MER)

Revenue means all revenue in the period, including customers who came through organic search, referrals or repeat purchases. Spend means everything marketing cost: ad budgets, agency fees, tooling, sometimes salaries. The wider the definitions, the more honest the ratio and the less it says about any single decision.

• MER is blended

  One number for the whole business. It cannot be inflated by a platform claiming a conversion another platform also claimed.

• ROAS is per channel

  Revenue attributed to one campaign or platform over its spend. It depends entirely on which attribution model did the attributing.

• They answer different questions

  MER: is marketing paying for itself this quarter? ROAS: should this campaign get more budget next week? A team needs both, and only one of them needs attribution.

A common pattern is a rising platform ROAS beside a falling MER. Each platform reports a better return while the business earns less per euro, because the platforms are each taking credit for the same customers. That gap is the case for attribution on CRM revenue, where one deal is credited once.

• A sanity check on attributionIf the sum of attributed revenue across channels is far above total revenue, the models are double counting. MER is the ceiling.
• Board-level reportingOne ratio a finance team can reproduce from the ledger, with no model to defend.
• Long sales cyclesFor a business whose deals close months after the click, a quarterly MER is often more stable than any weekly channel figure.

• It cannot tell you which channel to cut or scale. A falling MER with five channels running gives you five suspects.
• It lags. Revenue arrives after the spend, so a quarter's MER reflects last quarter's marketing as much as this one's.
• It rewards cutting. Reduce spend and MER rises for a while as pipeline built earlier keeps closing, which hides the damage until it is done.
• It mixes marketing revenue with everything else. Referrals and renewals lift MER without any campaign having earned them.

The practical setup is MER as the guardrail and per-channel revenue from marketing reporting software as the steering wheel. The ROAS calculator shows the break-even ratio for a given margin, which is the line the blended number must stay above.

MER is the one marketing return nobody can argue with, and the one that decides nothing on its own. Use it to check that the attributed numbers add up and that marketing as a whole clears its break-even, then use attribution on CRM revenue to decide where the next euro goes.