Measurement
MER vs ROAS: read the business result alongside the campaign
A practical example of why channel ROAS and total marketing efficiency answer different questions, and how to review them together.
Your ad accounts look healthy, but cash is tight. That does not automatically mean the platforms are wrong. It may mean the reports answer a narrower question than the one your business needs to answer.
ROAS compares attributed revenue with advertising spend. Marketing efficiency ratio, or MER, compares total business revenue with the marketing spend you choose to include. The precise spend definition matters: media-only MER and a ratio including creative production, tools and contractors are different measures. Label your version before comparing weeks.
Work through an example
Suppose a store records ₹600,000 in net revenue during a week. It spends ₹100,000 on Meta and ₹50,000 on Google. It also spends ₹30,000 on creative production and a marketing contractor.
| Measure | Calculation | Result |
|---|---|---|
| Media-only MER | ₹600,000 ÷ ₹150,000 | 4.00× |
| MER including the listed production costs | ₹600,000 ÷ ₹180,000 | 3.33× |
Now imagine Meta attributes ₹400,000 of revenue and Google attributes ₹300,000. Adding those attributed amounts gives ₹700,000, more than the store's total revenue. The same order may be credited by more than one channel under different attribution rules. That sum is not a new source of cash.
The numbers above are illustrative. They demonstrate why you should reconcile reporting definitions before reallocating budgets.
Give each measure a job
Use channel ROAS to investigate campaigns, creatives and audiences within the platform's reporting model. Use a consistently defined MER to ask whether the business is producing more revenue for the marketing resources it consumes. Use contribution after advertising to ask what remains after variable costs.
None of these proves incrementality by itself. Existing customers, organic demand, promotions and seasonality can all affect total revenue. A controlled experiment or an appropriate measurement design is needed to estimate what the advertising caused.
Diagnose the pattern, not one number
If channel ROAS rises while MER falls, check overlapping attribution, spend definitions and a shift toward returning customers. If MER rises while new-customer acquisition slows, the store may be harvesting existing demand rather than building the next cohort. If both improve while contribution falls, examine discounts, returns and product mix.
These are hypotheses to investigate, not automatic conclusions. Write down the observation, the suspected cause and the next check. That keeps the conversation grounded when a dashboard number is tempting you to act immediately.
Set up a weekly review
- Choose a revenue definition and timezone.
- Freeze a list of included marketing costs.
- Separate new and returning customers where the data supports it.
- Compare equivalent date ranges and allow for reporting delays.
- Review contribution margin alongside both ratios.
- Record one decision and its expected business effect.
Pair this review with the break-even ROAS worksheet and weekly Shopify scorecard. The useful question is not which ratio is universally better; it is what each one tells you about the decision in front of you.
Source
Shopify: marketing efficiency ratio. We use the general distinction between blended and channel measurement; the example, review sequence and diagnostic questions above are original editorial work.