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%
The marketing efficiency ratio formula
MER = total revenue ÷ total marketing spend. Both sides are deliberately blunt: all revenue (not platform-attributed revenue) and all marketing spend (media, agency fees, creative, tools). Worked example: a brand doing £412,000 of monthly revenue on £74,000 of media plus £14,600 of fees and creative has a MER of 412,000 ÷ 88,600 = 4.65×. No platform dashboard can inflate that number, because it reconciles to the bank.
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.
What is a good marketing efficiency ratio?
There is no universal benchmark, because the MER you need is set by your margins. A useful way to find your own floor: a brand with a 50% contribution margin whose marketing is 100% paid needs a MER above 2.0× just to break even on variable costs - the same logic as break-even ROAS, applied to the whole business. In practice most healthy ecommerce brands sit between 3× and 5×, with strong organic and repeat revenue pushing it higher. A rising MER at flat spend means efficiency is improving; a falling MER as spend scales is normal, and the question becomes whether the marginal revenue is still profitable.
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.
What is the marketing efficiency ratio formula?
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.
How often should you track MER?
Weekly is the sweet spot for decisions - daily MER is too noisy (revenue lags spend) and monthly hides problems for too long. Track it as a trailing 7- and 28-day figure, and investigate when the trend moves, not the single day.
MER tells you efficiency; it does not tell you profit. Pair it with the POAS calculator to see what you actually keep, find your floor with the break-even ROAS calculator, or see every metric explained in the glossary.