What is Blended ROAS?

Platform-reported ROAS is each ad network grading its own homework: Meta counts a sale if the buyer saw a Meta ad in the attribution window, and TikTok counts the same sale if they also saw a TikTok ad, so summing the dashboards overstates true return, often by 30 percent or more on overlapping audiences. Blended ROAS fixes this by ignoring attribution entirely and dividing your real total revenue by your real total ad spend for the period. It is closely related to MER (MER is the same idea, usually quoted as the raw ratio across all marketing including non-ad costs, while blended ROAS typically means revenue over paid media spend). The honest tradeoff: blended ROAS is the truth about whether your paid mix as a whole is profitable, but it is blind to allocation. It cannot tell you that your TikTok creative is carrying the account while your Google brand campaign is just harvesting demand you already paid to create. The standard 2026 workflow is to set a blended ROAS or MER floor as the spending guardrail, then run incrementality tests and read funnel metrics (3-second view rate, CTR, ATC) to decide which specific channels and creatives deserve the next dollar. Treat per-platform ROAS as a directional creative-ranking signal within a channel, never as a true profit number.