MER
Also: Marketing Efficiency Ratio
MER (marketing efficiency ratio) is total revenue divided by total marketing spend for a period, treating the whole marketing budget as one input. It is the same calculation as blended ROAS.
MER = Total revenue ÷ Total marketing spend
MER is the finance team's version of ROAS: immune to attribution disputes because it does not attribute anything. It answers whether marketing as a whole is efficient, and nothing about which channel deserves the next dollar.
Teams argue about MER versus ROAS when one is using total marketing spend and the other paid media only. Agree on the denominator first.
Go deeper: Blended ROAS / MER calculator
Related terms
In Roasy
Roasy computes this across every ad network, Adjust, and RevenueCat on one screen — real revenue, cohort windows, and the same definition everywhere.