MER

MER, the marketing efficiency ratio, is total net revenue divided by total advertising spend across every platform, both taken from your own books. One numerator and one denominator mean nothing can be double counted, which is what platform-reported ROAS cannot promise.

It cannot double count, because there is only one numerator. That makes it the honest counterweight to platform ROAS figures, which overlap and therefore add up to more revenue than you actually took. The full comparison of the three ratios is in MER, POAS or ROAS.

It will not tell you which campaign worked, and it is not meant to. It tells you whether the whole machine is running at a ratio you can afford, and what ratio you can afford is set by your CM2 margin, not by a benchmark.

Use net revenue rather than gross on top. Gross revenue still carries the VAT you never keep, which flatters the ratio by the whole VAT rate and makes two months with different return rates uncomparable.