Definition
Blended ROAS is your total revenue divided by your total ad spend across every channel. Unlike platform ROAS, it isn't built on attribution and therefore can't be double-counted.
Also called: Blended ROAS, aROAS, Total ROASSeveral channels can claim the same purchase.
All 100 purchases in this example are claimed by at least one channel. Adding channel reports counts shared purchases twice. MER uses store revenue and total marketing spend; it does not determine causal lift.
Why blended beats platform ROAS
Each platform credits itself with the same sales using its own generous windows, so the sum of Meta's, Google's and TikTok's reported ROAS describes a revenue larger than what actually came in. Blended ROAS ignores all attribution and looks only at the total: what came in, and what it cost.
Blended ROAS is closely related to MER. The difference is mostly whether the denominator is all marketing spend (MER) or only ad spend (blended ROAS). The point is the same: measure efficiency at a level no single platform can inflate.
Blended as a scaling compass
Its great strength is as a scaling test. Turn the budget up and watch blended ROAS: if it holds or rises, the growth was incremental. If it falls while the platform numbers still look great, you bought sales you'd have gotten anyway.
We steer by blended/MER at the top and use POAS and contribution margin to distribute the budget within. One tells you whether the machine as a whole is making money; the other, where inside the machine the euros should go.
Frequently asked questions
What's the difference between blended ROAS and MER?
Almost none — both measure the total without attribution. Blended ROAS typically has only ad spend in the denominator, while MER often counts all marketing spend (tools, agency). Neither can be inflated by a single platform.
Why is my blended ROAS lower than the platforms'?
Because the platforms double-count: each credits itself with the same sales. The blended reality (total revenue against total spend) is almost always lower, and it's the one that matches the money in the bank.
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Nicklas Segatz Mortensen
Growth hacker and fractional CMO with 10+ years' experience and hundreds of millions in managed ad spend behind him. Background from larger Danish and international scale-ups, and from the agency world.
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