MER (Marketing Efficiency Ratio)
Also known as: Marketing Efficiency Ratio, blended MER
Total revenue divided by total marketing spend at the account level.
MER answers the question every founder asks: 'we spent X, we made Y — is that good?' Where per-platform ROAS can double-count and view-through-attribute, MER is a single ratio you can defend to a CFO.
Definition
MER is a platform-agnostic ratio: all revenue over all marketing spend in the same period. Because it uses shop-level revenue, MER is immune to attribution changes and iOS signal loss.
Why it matters
MER is the CFO's north-star. Individual campaign ROAS can lie because of view-through windows and platform double-counting; MER is what the bank statement sees.
Formula
MER = Total Revenue ÷ Total Marketing Spend
| Revenue source | Spend source | Attribution risk | |
|---|---|---|---|
| Platform ROAS | Platform-attributed only | Single platform | High (view-through, dedup) |
| Blended ROAS | All paid-attributed | All paid | Medium |
| MER | All shop revenue | All marketing | Low |
MER vs ROAS vs [[blended-roas|Blended ROAS]]
ROAS is per-campaign as reported by the ad platform. Blended ROAS aggregates all paid spend against shop revenue attributable to paid. MER goes further — total revenue over total marketing spend, including retention marketing. As you move up the stack, numbers become truer but slower to react to.
$400,000 revenue in July on $110,000 total spend → MER = 3.6.
Common mistakes
- ✕Comparing MER week-over-week during promotional weeks.
- ✕Using MER for tactical decisions where campaign-level ROAS is more actionable.
- ✕Ignoring the organic revenue baseline when reading MER.