What Is Blended MER and Why Is It More Honest Than ROASUpdated 5 days ago

ROAS (Return on Ad Spend) is the metric most advertising platforms report by default — the revenue attributed to a specific campaign divided by the spend on that campaign. A 4x ROAS means four units of revenue were attributed for every one unit of ad spend.

The problem with ROAS is attribution. No advertising platform can attribute 100 percent of the revenue it contributed to generating. A buyer who saw a Facebook ad three days before searching directly and purchasing gets partially credited to multiple channels or fully credited to only one. ROAS can look excellent on a single platform while the business is losing money across the total marketing spend.

Blended MER (Marketing Efficiency Ratio) is a more honest measure:

• Total store revenue divided by total marketing spend across all platforms combined
• It does not care which channel gets attribution credit
• It measures the total return on all marketing investment together
• A blended MER of 3x means three units of revenue for every one unit of total marketing spend

What this changes in practice:

A store can have a 5x ROAS on Meta and a 3x ROAS on Google while its blended MER is 2x — meaning after accounting for combined spend across all channels, the business generates only two units of revenue per unit of total marketing investment. Blended MER is the number that tells the truth.