Meta ROAS and blended marketing efficiency ratio (MER) both compare revenue and advertising spending—but use different revenue sources. They should never be presented as the same thing.
Meta-attributed ROAS
ROAS = revenue attributed by Meta ÷ Meta ad spend. Meta uses attribution rules and event-tracking signals to identify purchases potentially influenced by ads. Its reported totals can differ from a merchant's order platform.
Blended MER
MER = total store revenue ÷ Meta ad spend. This shows overall revenue relative to Meta advertising spend, but isn't a causal measurement: store revenue can also include email, organic search, direct customers and other channels.
Example
Suppose Meta spend is $1,000, the Meta-attributed purchase value is $2,100, and total store revenue is $4,000. Then Meta ROAS is 2.1× and blended MER is 4.0×. The difference does not prove Meta underreported sales or that ads generated all store revenue.
Which metric should I act on?
Review both, but also consider contribution margin, refunds, logistics costs, attribution settings, and data completeness before reallocating budgets. Ad Pulse labels these measures separately and highlights areas that merit investigation.
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