Ad glossary
MER (marketing efficiency ratio)
Total revenue divided by total marketing spend across all channels, used as a blended view of marketing efficiency.
MER, or marketing efficiency ratio, compares all of your revenue with all of your marketing spend. It is sometimes called blended ROAS. Rather than trusting each ad platform's own attribution, MER takes a top-down view: how much did the business sell in total, and how much did it spend on marketing to get there?
How to calculate it
MER = total revenue ÷ total marketing spend
Worked example (made-up numbers): in a month your store records $60,000 in revenue. You spend $10,000 on Meta, $4,000 on Google and $1,000 on influencers, for $15,000 in total. MER = 60,000 ÷ 15,000 = 4.0.
Why marketers use it
Since Apple's App Tracking Transparency changes and wider browser privacy restrictions, platform-reported ROAS has become less complete. Different platforms also tend to claim credit for the same sale. MER avoids both problems because it is based on numbers from your own store and finance records.
Limitations
- MER does not tell you which channel or campaign is working, so it complements rather than replaces platform data.
- It includes revenue from repeat customers, email and organic traffic, which can flatter results; some teams track a new-customer version instead.
- It is a revenue ratio, not a profit ratio. Compare it with your contribution margin to see whether the business is actually making money.
A useful habit is to set a target MER based on margins, watch it weekly, and use platform data and incrementality tests to decide where to move budget.
Last reviewed Oct 27, 2026