MER: Marketing Efficiency Ratio
Total revenue divided by total marketing spend across all channels — a platform-agnostic efficiency measure that avoids last-click attribution bias.
Formula
Why it matters
MER is the eCommerce marketer's antidote to fragmented attribution. When Meta reports 4× ROAS and Google reports 3× ROAS, but your blended numbers only produce 2.5× MER — MER is telling you the truth. It captures all revenue against all spend, with no platform attributing the same purchase twice.
How to improve MER
Treat MER as the north star — individual channel ROAS can be sacrificed for overall MER improvement. Sometimes shifting spend from a "high ROAS" channel to a lower-ROAS channel raises total MER by improving cross-channel synergy.
DTC eCommerce: 3–6× is healthy. Above 6× may indicate under-investment in growth. Below 2× is typically unsustainable.
Prooflytics tracks MER automatically from your connected sources and flags it in your daily briefing when it moves significantly.
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Calculate Marketing Efficiency Ratio
MER
MER = Total Revenue ÷ Total Marketing Spend
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Frequently asked questions
What is the difference between MER and ROAS?
ROAS is reported per platform (Meta ROAS, Google ROAS) — each platform attributes revenue to its own clicks and pixels. MER is calculated independently: total Shopify/CRM revenue ÷ total ad spend. MER cannot be manipulated by platform attribution windows and gives a single source of truth across all channels.
What is a good MER for DTC eCommerce?
A healthy DTC brand targets MER of 3–6×. At 3×, one-third of revenue goes to marketing — sustainable for most categories. At 6×+, you are likely under-investing in growth. MER below 2× means marketing costs are consuming over half of revenue, which is unsustainable without strong gross margins.
Can I use MER alongside ROAS?
Yes — they answer different questions. ROAS tells you which campaigns and channels are most efficient for optimisation. MER tells you whether the total marketing spend is producing enough revenue for the business to be profitable. Use ROAS for day-to-day campaign decisions; use MER for weekly budget reviews.