Free tool
MER Calculator (blended ROAS)
MER compares your total revenue to your total ad spend. It is the one acquisition metric attribution cannot distort.
MER (marketing efficiency ratio), also called blended ROAS, is the ratio of total company revenue to total advertising spend across every channel. Unlike platform ROAS, it depends on no attribution window and no pixel.
The share of advertising in your revenue
How MER is calculated
MER = Total revenue ÷ Total ad spend
120,000 € of revenue on 20,000 € of advertising gives a MER of 6.0: every euro of media sits alongside 6 € of revenue. Read the other way, advertising is 16.67 % of revenue.
Why it matters more every year: the sum of the ROAS figures platforms report almost always exceeds real revenue, because two platforms claim the same sale. MER cannot lie that way, since its numerator comes from the accounts rather than from a pixel.
⚠️ Its weakness mirrors its strength: it does not say which channel works. It decides the overall level of spend, not how to split it. The two readings complete each other, neither replaces the other.
How to read it
- As a trend, never in absolute terms. A MER of 6 is only good or bad against your own MER last month, at an identical cost structure.
- Against your margin. A MER of 6 at 30 % margin leaves 20 % of revenue after media; the same MER at 15 % margin covers nothing. The threshold is worked out in the break-even ROAS calculator.
- When you scale budget. It is the best saturation detector there is: if spend rises and MER falls, the extra euros are buying a less profitable audience.
Frequently asked questions
What is the difference between MER and ROAS?
ROAS is attributed: it compares the revenue a platform claims to that platform’s spend. MER compares TOTAL revenue to TOTAL spend, with no attribution. That is why MER is always lower, and more reliable.
What is a good MER?
There is no universal value: it depends on margin, on the share of repeat customers and on brand maturity. A business with heavy repeat purchase shows a high MER without advertising doing much of the work.
Should platform ROAS be dropped?
No. ROAS is still the tool that arbitrates between two campaigns inside one platform. MER arbitrates the total level of spend. Using one for the other’s job is what produces wrong decisions.
MER falling while your ROAS figures climb?
That is the classic signal of double attribution between platforms, or of a budget past its audience saturation point.
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