The formula
- MER = total revenue ÷ total marketing spend
- Acquisition MER (aMER) = new-customer revenue ÷ total marketing spend
- Break-even MER = 1 ÷ contribution margin
- Contribution after marketing = revenue × margin − marketing spend
How to use it
- Use store revenue from Shopify or your backend, not platform-attributed revenue — that is the point of MER.
- Include every marketing cost in the period: all ad platforms, agencies, influencers and tools.
- Track acquisition MER next to MER. A rising MER with a falling aMER usually means returning customers are carrying the numbers.
Worked example
$250,000 of store revenue and $60,000 of total marketing spend give a 4.17× MER; marketing is 24% of revenue. $120,000 came from new customers, so acquisition MER is 2.0×. At a 50% contribution margin the break-even MER is 2.0× and $65,000 is left after marketing.
Questions
What is MER in marketing?
Marketing efficiency ratio: total revenue divided by total marketing spend. It ignores attribution, so it cannot double-count the way platform ROAS does.
What is the difference between MER and ROAS?
ROAS divides one platform’s attributed revenue by that platform’s spend. MER divides all revenue by all marketing spend. ROAS tells you where to move budget; MER tells you whether marketing as a whole pays.
What is acquisition MER?
Revenue from new customers divided by total marketing spend. It strips out returning-customer revenue that marketing did not have to buy.
What is a break-even MER?
1 ÷ contribution margin, the same math as break-even ROAS but applied to the whole business.