Cloud Ten / MER calculator
MER calculator: one number your platforms cannot inflate.
Calculate your marketing efficiency ratio and see how much revenue your platforms are double-counting. Total revenue divided by total spend, adjusted for margin.
If your platforms claim more revenue than the business made, the difference is double-counting.
What is marketing efficiency ratio?
MER is total revenue divided by total marketing spend. One number over the top of everything, using figures from your accounts rather than from an ad platform reporting on itself.
Why MER exists
Every channel claims the same conversion. Add up what Meta, Google and TikTok each say they produced and the total routinely exceeds what the company actually banked. MER cannot double-count.
What MER will not tell you
It cannot say which channel deserves credit, and it counts revenue that would have arrived anyway. Use it as the headline number and incrementality testing to find what advertising genuinely added.
How to calculate MER for an eCommerce brand
Take total revenue for the month from Shopify or your accounts, not the sum of what each platform claims. Take total marketing spend for the same month: every ad platform, plus agency fees, creative and tooling if you want the honest version. Divide. £400,000 of revenue on £80,000 of spend is an MER of 5.0. Then hold it against your break-even: on a 30% contribution margin, 3.3 is where you start making money.
MER, aMER and blended ROAS
Blended ROAS is the same calculation as MER under a different name. aMER, acquisition MER, narrows it to new-customer revenue over acquisition spend, so returning customers stop flattering the number. Track both: MER for the board, aMER for whether acquisition is actually working. For what a single channel made in profit, use POAS.
Frequently asked
What is MER?
Marketing efficiency ratio: total company revenue divided by total marketing spend across every channel. Unlike platform ROAS it cannot double-count, because it uses one revenue figure and one spend figure.
How do I calculate MER?
Divide total revenue for the period by total advertising spend for the same period. 400,000 of revenue on 80,000 of spend is an MER of 5.0.
How do I calculate MER for eCommerce?
Use Shopify or your accounts for revenue, never the platforms. Add up spend across Meta, Google, TikTok and anything else for the same period, include agency and creative costs if you want the honest version, and divide revenue by spend.
What is a good MER?
It depends on margin. A 70% margin brand can thrive at 3.0; a 25% margin brand needs 5.0 or more. Compare MER to your break-even, not to another company.
What is aMER?
Acquisition marketing efficiency ratio: new-customer revenue divided by acquisition spend. It strips out returning customers who would have bought anyway, so it is a harder, more honest test of whether paid media is winning new business.
Is MER the same as blended ROAS?
Yes. Blended ROAS and MER are the same ratio, total revenue over total ad spend. MER is the name finance teams tend to use.
MER or ROAS?
Both. ROAS compares ads within a channel. MER tells you whether the whole marketing operation is working, which is the question a finance director asks.
How often should I look at MER?
Weekly for direction, monthly for decisions. Daily MER swings with order timing and spend pacing, and reacting to it is how budgets get cut on a Tuesday for no reason.