What Is MER (Marketing Efficiency Ratio)?
MER — also called Blended ROAS — is the simplest and most honest measure of marketing efficiency. It divides your total business revenue by your total marketing spend across every channel.
Unlike platform-reported ROAS, MER does not suffer from attribution overlap. When Meta, Google, and TikTok all claim credit for the same purchase, MER cuts through the noise with a single ground-truth number.
If you add your COGS, this calculator also shows your contribution margin after marketing — the actual dollars left after product costs and ad spend. This is the number that determines whether your growth is profitable.