Meta says 4.2x. Google says 6.8x. Your bank says something less flattering. Someone is grading their own homework.
The short answer
Platform ROAS attributes every sale to whichever platform claimed it - sum them and you'll exceed actual revenue by 30-60%. Blended ROAS (total revenue / total spend) cannot flatter anyone, which is why it should trigger every budget decision. Use platform numbers for directional optimization inside channels; use blended MER and contribution margin for allocation across them.
Directional, optimistic
Best for: Week-to-week creative and bid decisions inside a single channel
Typical cost: Free - but the bias is priced in
The truth serum
Best for: Budget allocation, scaling decisions, board reporting
Typical cost: Free - requires honest accounting
When deciding whether to scale a campaign
Pick Blended first, platform second
When choosing between two ad variations
Pick Platform data
When reporting to investors or partners
Pick Blended, always
When platforms' claims diverge wildly
Pick Trust the blend
Our verdict
Every dashboard we build leads with blended metrics so no platform grades its own homework. Platform ROAS remains useful for steering inside a channel - just never let it steer the budget across channels. That job belongs to contribution margin.
It depends entirely on margin. At 70% gross margin, blended ROAS of 2x can be strongly profitable; at 20% margins you may need 5x+. Compute your break-even ROAS first - everything else is commentary.
Triangulate like we do on every account: platform numbers for direction, blended MER for truth, and periodic geo-holdout or incrementality tests to calibrate how much each platform's claims to discount.
More comparisons
Book the free audit - we will model both paths on your actual numbers in one call.