ROAS vs. MER: Why Blended Metrics Win in 2026
Return on Ad Spend is dying as a decision-making metric. Here's why blended MER and contribution margin are how serious D2C and B2B brands run their P&L now.
Platform ROAS lies to you
Meta, Google and LinkedIn each over-attribute conversions to themselves. Add them up and your reported ROAS often exceeds 100% of your revenue. MER — total revenue divided by total ad spend — is the single number that can't lie, because there's only one revenue figure.
The MER + CM double-check
Run MER weekly. Run contribution margin (CM = revenue – COGS – ad spend – shipping) monthly. If MER is up but CM is flat, you're scaling unprofitably. If CM is up but MER is flat, you've found pricing or product leverage.
How to set up incrementality tests
Pause a channel in one geo for two weeks. Compare lift vs. a matched control. This is the only honest way to know if a channel is contributing or just claiming credit.
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