MER, sometimes called blended ROAS, compares all revenue to all ad spend. It exists because platform-reported returns overlap: two channels can each claim the same conversion, and the sum of what they claim can exceed what the business actually sold.
How to calculate MER
A worked example
A brand spends $250,000 across paid social, search, and rewarded placements in a month and books $1,000,000 in revenue:
Meanwhile the ad platforms between them report $1,400,000 in attributed revenue. That $400,000 gap is double-counting, and it is the whole reason MER exists.
What counts as a good MER?
It is set by your margin. A brand at 70% gross margin survives on a far lower MER than one at 30%.
Growth stage matters. Deliberately buying market share suppresses MER and may still be the right call.
Organic mix moves it. Strong organic and returning revenue lifts MER without any change in advertising performance.
Trend beats level. MER falling while spend rises is the classic signal that a channel has run out of efficient audience.
MER vs. ROAS
ROAS is per-campaign and uses attributed revenue, so it answers which ad worked. MER is business-wide and uses actual revenue, so it answers whether marketing as a whole is paying for itself. The pattern worth knowing: platform ROAS climbing while MER stays flat usually means channels are competing for credit on conversions that were already going to happen.
How to use it
Treat it as a health check, not a targeting tool. MER cannot tell you which campaign to cut.
Pair it with incrementality. Incrementality testing is what turns a suspicious MER into a decision.
Watch it when adding a channel. A new channel that lifts attributed revenue but not MER is mostly reallocating credit.
Hold the definition steady. Changing what counts as revenue or spend mid-year makes the series useless.
Common mistakes to avoid
Including non-advertising marketing cost inconsistently. Agency fees and tooling either count every month or never.
Comparing your MER to another company's. Margin structure and organic strength make the comparison meaningless.
Using MER to judge a channel. It is an aggregate by construction and says nothing about any single line item.
Frequently asked questions
Q: How is MER different from ROAS?
Q: What is a good MER?
Q: Can MER tell you which channel to cut?
Keep reading
Metric
ROAS (Return On Ad Spend) measures the revenue generated for every dollar spent on advertising. It is a direct read on whether a campaign is paying for itself.
Metric
ROI (Return On Investment) measures the profitability of an investment as a percentage. Because it is a ratio rather than a dollar amount, it makes it easy to compare very different investments.
Concept
Performance marketing is advertising where advertisers pay only for measurable results, such as installs, leads, or sales, rather than for exposure. It is priced on outcome-based models and tracked with postbacks and measurement partners. This makes spend directly accountable to results.