MER
Total revenue divided by total ad spend across every channel: the whole-business scoreboard.
MER, the marketing efficiency ratio, is your total revenue divided by your total advertising spend across every channel. Where platform ROAS measures one campaign, MER measures the whole business: it counts every sale once and cannot be double-claimed by two platforms that both touched the same buyer.
MER is the business scoreboard; platform ROAS is the steering wheel. MER tells you whether advertising is profitable overall, and ROAS tells you which lever to pull. Its blind spot is that it blends everything, so it flags that the account is slipping without telling you which campaign is responsible. A MER that holds while you scale is the real win; a MER drifting toward your break-even is the early warning that paid is working harder for the same revenue.
Read MER vs ROAS for when to use each, and see how clean web analytics make the blended number trustworthy. MER is also called blended ROAS.
Put the number to work: the break-even ROAS calculator turns your margins into the ROAS you need, and a free Due Diligence Audit checks whether the figures you see are the ones you are getting. Back to the glossary.