MER calculator

MER is total business revenue divided by total marketing spend, across every channel and regardless of attribution. Eighty thousand of revenue on sixteen thousand of spend is a MER of 5× — marketing costing 20% of revenue.

MER became popular precisely because platform-reported ROAS stopped being trustworthy. After privacy changes broke deterministic tracking, the sum of every channel claimed revenue routinely exceeds actual revenue, sometimes by a wide margin. MER sidesteps the problem by refusing to attribute anything: it compares what the business took against what the business spent. The trade-off is that it cannot tell you which channel to cut, so most teams use MER for the health of the whole and platform metrics for relative decisions within it.