Paid Media
MER (Marketing Efficiency Ratio)
Quick definition
Total revenue divided by total marketing spend across all channels. The cleanest profitability proxy at the business level.
What it actually means
MER avoids the attribution circus by ignoring platform-reported ROAS entirely. If you spent $100k on all marketing this month and revenue was $400k, MER is 4. That example is the maths, not a target. MER often trends down as spend scales because incremental returns get harder. MER is the metric many DTC operators and Shopify Plus brands report when they want a channel-agnostic view of efficiency.
Related terms
ROAS (Return on Ad Spend)
Revenue generated divided by ad spend. A 4x ROAS means $4 in revenue for every $1 spent.
CAC (Customer Acquisition Cost)
Total marketing spend divided by new customers acquired in the same period.
LTV (Customer Lifetime Value)
The total revenue a customer generates over their entire relationship with your brand.