Free tool
MER calculator
The one honest number you can run the business on. Total revenue ÷ total spend, blended across every channel - no platform inflation.
MER (Marketing Efficiency Ratio) = total revenue ÷ total marketing spend, blended across every channel. The honest number you can run the business on.
Marketing Efficiency Ratio (MER)
- For every £1 on marketing
- £4.65 revenue
- Marketing as % of revenue
- 21.5%
Why MER beats platform ROAS
When Meta and Google both take credit for the same purchase, your reported ROAS adds up to more revenue than you actually made. MER side-steps that entirely: one number, all spend, real revenue. It is the figure to optimise the whole account against - then use POAS to check you are keeping profit, not just generating revenue.
Frequently asked questions
What is MER (Marketing Efficiency Ratio)?
MER is total revenue divided by total marketing spend across every channel. Unlike platform ROAS - where Meta and Google can both claim credit for the same sale - MER is one blended number reconciled to your actual revenue, so it cannot be double-counted or inflated.
How do you calculate MER?
MER = total revenue ÷ total marketing spend. If you made £412,000 in revenue on £88,600 of total marketing spend, your MER is 4.65× - for every £1 of marketing, you generated £4.65 of revenue.
MER vs ROAS - what is the difference?
ROAS is reported per platform and is prone to over-attribution (each platform marks its own homework). MER is blended across all channels and tied to real revenue, which makes it far harder to fool. Most operators run the business on MER and use ROAS only as a channel-level diagnostic.
What is a good MER?
It depends on margin and business model, but many ecommerce brands target a MER of 3-5×+. The more useful question is whether your MER clears the blended efficiency you need to be profitable after all costs - pair it with your POAS and break-even ROAS to know.