Marketing efficiency ratio (MER)

Marketing efficiency ratio is a blended, business-level measure of marketing performance, calculated as MER = total revenue / total marketing spend, using revenue and spend summed across every channel rather than any single campaign. An MER of 4, for example, means every dollar of marketing spend was associated with four dollars of revenue.

MER is deliberately platform-agnostic, unlike return on ad spend, which is usually calculated per channel or per campaign from that channel's own reported, and often overstated, conversion data. Because MER does not depend on any one platform's attribution, it is less distorted by attribution overlap, where several channels each claim credit for the same sale, and it is often used as a sanity check against a set of channel-level ROAS figures that, added together, would imply more revenue than the business actually generated.

MER matters most to finance and leadership as a single top-line efficiency number, alongside metrics like Blended CAC and the LTV:CAC ratio, but its simplicity is also its limitation: because it aggregates every channel together, it cannot show which specific channel is efficient and which is dragging the average down, and it says nothing directly about the marginal cost per acquisition of the next dollar spent. It works best paired with channel-level metrics rather than in place of them.