MER Calculator
Divide all your revenue by all your ad spend to see marketing efficiency at the business level.
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What is MER?
MER, short for Marketing Efficiency Ratio, is total revenue divided by total ad spend. It looks at the business as a whole rather than at individual campaigns.
Where ROAS measures the revenue a campaign claims for itself, MER counts all revenue entering the business while you were advertising. That makes MER far less dependent on the accuracy of attribution models than ROAS is.
How it is calculated
MER = Total Revenue ÷ Total Ad Spend
Divide total revenue for the period by total ad spend across every channel in that same period. On the revenue side, include all sales rather than only attributed ones.
Include every channel on the spend side too. Leaving one out means counting the revenue it produced while ignoring its cost, which inflates MER artificially.
How to read the result
MER holds the total picture together even when channels overlap in attribution. If the revenue your platforms report adds up to more than your actual sales, MER is the more trustworthy reference.
In exchange, MER cannot tell you which channel is working. Using ROAS for channel decisions and MER as an overall health check keeps each in its proper place.
Frequently asked questions
What is the difference between MER and ROAS?
ROAS divides the revenue attributed to a campaign by that campaign’s spend. MER divides the whole business’s revenue by total ad spend. ROAS informs channel decisions; MER measures overall efficiency.
Does organic revenue belong in MER?
Yes, the standard definition uses total revenue including organic sales. That lets MER reflect cases where advertising feeds organic demand, though a revenue spike unrelated to ads can also lift it misleadingly.
How often should MER be measured?
Daily measurement is noisy, because purchase decisions can land days after the ad. Weekly or monthly intervals make the trend far easier to read.