ROAS to MER Converter
Turn platform-reported ROAS into your true blended marketing efficiency ratio.
Your platforms claim 5.00× but blended MER is only 4.00×, about 25.0% of over-reporting. Scale to the MER, not the pixel.
MER (Marketing Efficiency Ratio) counts total revenue against total spend, so it can't double-count the way per-platform ROAS does.
About this calculator
A platform will happily tell you it drove a 5x ROAS while your bank account tells a different story, because every channel measures against its own pixel, and those pixels overlap. This calculator sets platform-reported ROAS side by side with your real total revenue and total spend, so you can see exactly how much of that reported number is double-counted credit rather than incremental sales.
How to use it
- Enter total revenue from all sources for the period, pulled from your store or finance system, not any single ad platform.
- Enter total marketing spend across every channel for that same period.
- Enter the ROAS your ad platform is reporting for its own campaigns.
- Compare true blended MER against the platform-claimed figure, and read the over-claim percentage and attribution gap to see how much the pixel is inflating reality.
Methodology
True blended MER (Marketing Efficiency Ratio) is total revenue ÷ total spend, a single number computed from company-wide totals that cannot double-count, since there is only one revenue figure and one spend figure.
Platform-claimed revenue is back-calculated as platform-reported ROAS × total spend, showing in dollar terms what the platform is implicitly asserting it generated.
The over-claim percentage is how far platform-claimed revenue exceeds your real total revenue, and the attribution gap is that same comparison in currency, claimed minus real.
Above roughly 15% over-claim, the calculator flags the platform number as inflated. That threshold is a practical heuristic, not a law, some overlap between channels is normal and expected, but persistent large gaps mean you are scaling budget against a number that overstates what you are actually getting.
FAQ
ROAS is measured per-platform using that platform's own pixel and attribution window, which credits itself for conversions that other channels (or organic, or direct) also touched. MER is measured once, at the company level, using real revenue and real spend, so it cannot suffer from that overlap.
MER. Platform ROAS is useful for relative, within-platform decisions (this ad set beats that one), but it is not trustworthy as an absolute number for deciding how much total budget the business can support.
A modest gap is normal, multiple channels legitimately assist the same conversion. A gap that keeps growing, or one that is large across every platform simultaneously, usually signals last-click attribution inflation rather than genuine incremental performance.
Monthly, at minimum, and any time you materially shift channel mix. The over-claim percentage tends to drift as spend shifts toward channels with looser attribution windows, so it is worth tracking as a trend, not a one-time check.