MER
Marketing Efficiency Ratio
Quick definition
Marketing efficiency ratio (MER) compares all revenue with all marketing spend for a period, without trying to credit individual campaigns.
Formula
MER = Total Revenue ÷ Total Marketing Spend
Formula variables
- Total Revenue
- All revenue for the period, not only revenue attributed to marketing. State whether it is gross or net of refunds.
- Total Marketing Spend
- The marketing costs included in the ratio. Define the scope explicitly, for example paid media only, or paid media plus agency and creative costs.
Worked example
- Total revenue
- $400,000
- Total marketing spend (paid media plus agency and creative costs)
- $100,000
400,000 ÷ 100,000
Result: 4
Each unit of total marketing spend corresponds to 4 units of total revenue. In this example the denominator includes paid media, agency fees and creative production; a paid-media-only denominator would give a different ratio.
How definitions differ
- Denominator scope
- Some teams include every marketing cost; others divide by paid media spend only. The ratio changes with the denominator, so compare MER only when the scope matches.
- Related names
- Some teams call a similar measure media efficiency ratio, and some call total revenue over total ad spend blended ROAS. Which costs are in the denominator differs between teams, so these are not guaranteed to be the same calculation as the one on this page. Check the denominator before treating them as equivalent.
How to interpret it
MER is a blended, top-down view. Because it does not depend on campaign-level attribution, it is not affected by tracking gaps in the way platform-reported ROAS is.
The same property is its weakness: it cannot say which campaign or channel produced the result, and revenue from repeat customers or organic demand is included.
When it is useful
- Tracking overall marketing efficiency when attribution is unreliable or fragmented.
- Comparing overall efficiency month to month alongside channel-level ROAS.
- Sense-checking the sum of platform-reported results against total revenue.
Limitations
- It does not say which channel or campaign is responsible.
- Revenue from existing customers and non-marketing sources is included.
- The ratio is not a profit measure and says nothing about margins.
Common mistakes
- Comparing MER across companies or periods with different spend definitions.
- Using MER to judge a single campaign.
- Treating MER and ROAS as interchangeable.