MER Calculator
Marketing efficiency ratio — total revenue over total marketing spend — and the attribution inflation factor that shows how much more your platforms claim than the business actually earned.
MER Calculator
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What this result does not account for
- No channel-level visibility — cannot direct budget between channels.
- Blends new and returning customer revenue together.
- Sensitive to revenue that marketing did not influence at all.
In short: Platforms claim more than the business earns. Meta and Google together report 113,872.50 of revenue against 96,000 actual — an inflation factor of 1.1862. MER of 3.0476 is the figure that cannot be inflated.
Formula
MER = total revenue ÷ TOTAL marketing spend
inflation = Σ(channel spend × reported ROAS) ÷ actual revenue
[('MER', 'no attribution, both inputs are yours'), ('blended ROAS', 'media spend only — a different number'), ('inflation factor', 'claimed revenue over actual'), ('break-even MER', '1 ÷ contribution margin, as always')]
Worked Example
- Total every marketing cost, not just media.
- Divide total business revenue by it.
- Sum each platform's claimed revenue separately.
- Divide claimed by actual for the inflation factor.
- Compare MER against one over contribution margin.
96,000 of revenue over 31,500 of total marketing spend — 24,975 media plus 6,525 of agency and tooling — is an MER of 3.0476x. Blended ROAS on media alone reads 3.8438x, 0.7962 higher, purely because it omits the non-media cost. Meanwhile Meta claims 63,000 and Google 50,872.50, totalling 113,872.50 against 96,000 actual — an inflation factor of 1.1862, or 18.6172% over-attribution. Break-even MER at a 42% margin is 2.3810x, so the programme clears it and marketing runs at 32.8125% of revenue.
Strengths & Limits Of This Model
Where this engine is strong
- Uses no attribution, so platforms cannot inflate it
- Separates MER from blended ROAS explicitly
- Quantifies attribution inflation as a tracked factor
Where it stops
- No channel visibility
- Blends new and repeat revenue
Practical Use Cases
Board reporting
One efficiency number that ties to the P&L.
Measuring attribution inflation
Comparing claimed revenue against actual.
Scaling decisions
Steering total spend by a figure platforms cannot inflate.
Judging the whole programme
Including agency, creative and tooling costs.
Setting a spend ceiling
Working from marketing as a share of revenue.
Methodology & Editorial Standards
Marketing efficiency ratio divides total business revenue by total marketing spend including non-media costs, and blended return on ad spend is computed alongside on media alone so the difference between the two names is explicit rather than assumed. The attribution inflation factor sums each channel's claimed revenue and divides by actual, which quantifies double-counting directly. Break-even MER uses the same reciprocal of contribution margin as break-even ROAS, applied at the business level rather than the campaign level.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
MER Calculator — 10 Expert FAQs
10 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What is MER?
Marketing efficiency ratio — total business revenue divided by total marketing spend over the same period. It uses no attribution at all, because both figures come from your own records rather than from a platform reporting on its own performance.
Is MER the same as blended ROAS?
Not quite, and the distinction matters in a board pack. Blended ROAS divides revenue by media spend only; MER divides by total marketing spend including agency fees, creative production, influencer payments and software. The gap widens the more agency-heavy your mix is.
Why is my platform ROAS higher than my MER?
Because each platform claims credit for conversions that other channels also influenced, and because MER's denominator includes spend the platform knows nothing about. Summing attributed revenue across channels routinely exceeds actual revenue by a substantial margin.
What is attribution inflation?
The ratio of what your platforms collectively claim to what the business actually earned. A factor above one means over-attribution. Tracking it over time is more useful than the level itself — a widening gap means your dashboards are becoming less reliable.
What is a good MER?
Above your break-even, which is one divided by contribution margin — the same reciprocal that governs break-even ROAS, applied at the business level. Published benchmarks are only useful as a sanity check, because they blend businesses with wildly different margins.
Should I use MER instead of ROAS?
Use both for different jobs. Platform ROAS is the right signal for optimising inside a channel, where relative performance is what matters. MER is the right signal for deciding total spend, because it is the only figure that cannot be inflated by attribution.
What is MER's biggest weakness?
No channel-level visibility. It tells you the machine is efficient or inefficient and nothing about which part is working, so it cannot direct budget between channels on its own. It also blends new and returning customer revenue together.
Why did MER become important?
Because platform attribution degraded sharply once tracking restrictions limited cross-app measurement. Reported figures drifted away from reality and platforms began modelling conversions they could not observe, so operators moved to a metric that never asks a platform anything.
Should MER include organic revenue?
Yes — that is the point. MER measures whether the whole revenue base justifies the whole marketing investment, and paid activity influences organic and direct sales in ways attribution cannot capture. Excluding organic would reintroduce exactly the attribution problem MER avoids.
What is aMER?
Acquisition MER — new customer revenue divided by total marketing spend. It strips out the repeat purchases that can make a blended figure look healthy while acquisition efficiency quietly deteriorates, and it requires clean new-versus-returning customer data to compute.