ROAS tells you what a single platform thinks it earned. MER (Marketing Efficiency Ratio) tells you what your whole business actually earned per euro of marketing. MER = total revenue ÷ total marketing spend. Because every ad platform claims credit for overlapping sales, the sum of your ROAS figures always looks better than reality. MER cuts through that inflation with one number you cannot fake — and for anyone spending across Meta, Google and TikTok at once, it is the metric that decides whether you are truly profitable.
What is ROAS, and where it breaks down
ROAS (return on ad spend) is revenue attributed to a platform divided by that platform spend. It is essential for judging one channel. The problem starts when you run several channels: Meta claims a sale, Google claims the same sale, and your email tool claims it too. Add the platform ROAS figures up and you appear to be printing money while your bank balance says otherwise. This is attribution overlap, and it gets worse the more channels you add.
What is MER?
MER — Marketing Efficiency Ratio, also called blended ROAS — is your total revenue divided by your total marketing spend across every channel. It ignores attribution entirely. If you did 100,000 EUR in revenue and spent 25,000 EUR across all ads, your MER is 4.0. There is no double-counting because there is only one revenue figure and one spend figure.
MER = Total revenue ÷ Total marketing spend
MER vs ROAS: a side-by-side
| Platform ROAS | MER (blended) | |
|---|---|---|
| Scope | One platform | Whole business |
| Based on | Attribution models | Real revenue and spend |
| Double-counts sales? | Yes, across channels | No |
| Best for | Diagnosing a channel | Judging overall profit |
| Can be inflated? | Easily | Almost never |
What is a good MER?
The same profit logic as ROAS applies: your MER must clear 1 ÷ your gross margin. With a 40% margin, break-even MER is 2.5, so you want an MER comfortably above it. See how to calculate break-even ROAS — the same number is your break-even MER. Many profitable e-commerce brands run an MER of 3 to 4; premium, high-margin brands can thrive lower.
How to use MER and ROAS together
- MER is the scoreboard. Track it weekly. If MER holds steady or improves as you increase spend, you are scaling profitably. If MER falls as spend rises, you are buying unprofitable growth.
- ROAS is the diagnostic. When MER dips, drop into platform ROAS to find which channel is dragging — a fatigued Meta account, a wasteful Google campaign, an untested TikTok launch.
- Let cheap channels look “bad” on purpose. A top-of-funnel prospecting channel may run below its own break-even while lifting overall MER by feeding a highly profitable retargeting channel. MER catches that; siloed ROAS punishes it.
- Watch the incrementality trap. Branded search and retargeting often show sky-high ROAS but capture demand you already had. MER keeps you honest about whether new spend creates new revenue.
Why blended reporting is hard — and worth it
To track MER you need total spend and total revenue in one place, refreshed often. That means pulling numbers from Meta, Google, TikTok and LinkedIn and reconciling them against your store revenue. Most teams do it in a messy spreadsheet once a month, far too late to act on. A cross-platform reporting view that updates continuously turns MER from a monthly autopsy into a daily steering wheel.
Frequently asked questions
What is MER?
Marketing Efficiency Ratio — total revenue divided by total marketing spend across all channels. Also called blended ROAS.
How is MER different from ROAS?
ROAS is per-platform and attribution-based, so channels double-count sales. MER is account-wide and based on real totals, so it cannot be inflated.
What is a good MER?
Any MER above your break-even (1 ÷ gross margin). A 40% margin needs an MER above 2.5; many brands target 3 to 4.
Should I optimise for MER or ROAS?
Both — MER for whole-business profit, ROAS to diagnose individual channels.
Adfure reports your blended MER alongside per-platform ROAS from your own connected accounts — so you see whole-business profit and the channel causing any change. Get your free AI audit or explore the platform.