Platform ROAS says you are winning. Your bank account disagrees. Use MER.
Every channel reports a profitable ROAS, the totals do not add up to your actual revenue, and you cannot tell whether spending more is making you money.
4 min read
Add up the revenue your ad platforms claim. Compare it to the revenue in your store. For most brands spending across Meta and Google, the first number is 20% to 60% larger than the second.
This is not fraud and it is not incompetence. Each platform reports conversions it believes it influenced, using its own window and its own rules, with no knowledge of what the other platform claimed. Double-counting is structural.
Marketing efficiency ratio — MER, sometimes called blended ROAS — sidesteps the whole argument by refusing to attribute anything.
The calculation, and why its crudeness is the point
MER is total revenue divided by total advertising spend. That is the whole formula.
Total revenue means everything the store took, from every source: paid, organic, email, direct, returning customers, the lot. Total ad spend means everything you paid the ad platforms across every channel.
If you took $180,000 in revenue and spent $45,000 on ads, your MER is 4.0. No attribution model was consulted. No window was chosen. No platform got to grade its own homework.
What a healthy MER looks like
There is no universal target, because MER has to clear your gross margin before it means anything. The floor is arithmetic:
| Gross margin | Break-even MER | Comfortable target |
|---|---|---|
| 30% (low-margin, resale, electronics) | 3.3 | 4.5 and above |
| 50% (typical apparel, home) | 2.0 | 3.0 and above |
| 70% (supplements, skincare, digital-adjacent) | 1.4 | 2.2 and above |
| 85% (software, high-margin consumables) | 1.2 | 1.8 and above |
Two adjustments matter for real businesses. First, in markets with high return-to-origin rates, use delivered revenue rather than orders placed — a 25% return rate turns a 3.0 MER into a 2.25 MER. Second, if a large share of your revenue is from returning customers who would have bought anyway, your MER flatters your acquisition efficiency. Track new-customer MER separately if you can.
When platform ROAS is still the right tool
MER is not a replacement for platform reporting. It is a different instrument for a different altitude, and using it for everything is as much a mistake as using platform ROAS for everything.
Platform ROAS is directionally valid for comparisons within one platform, over the same period, on the same attribution setting. Ad set A at 3.1 and ad set B at 1.4 in the same campaign is real information, even if both absolute numbers are inflated, because the inflation applies to both.
| Decision | Instrument |
|---|---|
| Which ad set to pause | Platform ROAS, within-platform comparison |
| Which creative to scale | Platform ROAS plus creative-level cost per purchase |
| Whether to increase total budget | MER trend over 14–28 days |
| Whether a new channel is working | MER before and after adding it, held over several weeks |
| Whether the business is profitable | Contribution margin, which is MER plus your real costs |
The scale test that actually works
The most reliable way to know whether more spend produces more profit does not involve attribution at all. Increase total spend by 20% and hold it there for two weeks. If MER holds roughly flat, the extra spend is finding real incremental customers. If MER falls in proportion to the spend increase, you are paying more for customers you were already getting.
This is slow, unglamorous, and considerably more trustworthy than any dashboard.
How to track MER without building a data warehouse
A spreadsheet with four columns run weekly beats a sophisticated dashboard that nobody updates.
- Week ending date
- Total store revenue, net of refunds
- Total ad spend across every platform
- MER — column two divided by column three
Add a fifth column for new-customer revenue if your store reports it, and a sixth for the ratio between platform-claimed revenue and actual revenue. That sixth column is an early-warning system: when the ratio jumps, either your tracking changed or your channel mix shifted toward view-through-heavy placements.
Review it weekly. Make budget decisions on the four-week trend, not the last three days. Most of the damage done to D2C brands by paid media comes from reacting to noise at the daily level.
Common questions
What is the difference between MER and blended ROAS?
In common usage they are the same calculation: total revenue divided by total advertising spend. Some teams reserve blended ROAS for paid-attributable revenue only, which reintroduces the attribution problem MER exists to avoid. If in doubt, use total revenue.
Is a MER of 3 good?
It depends entirely on gross margin. At 50% margin, a MER of 3 is healthy. At 30% margin it is barely above break-even before any fixed costs. Compute your break-even MER as 1 divided by gross margin, then judge.
Should I stop looking at platform ROAS?
No. Platform ROAS is still valid for comparing ad sets and creatives within the same platform and period. It stops being valid the moment you use it to judge total business performance or to compare across platforms.
How does MER handle organic and email revenue?
It includes them, deliberately. That is what makes it honest about the whole operation, and it is also why a rising email program improves MER without any change in ad performance. Track new-customer MER alongside it to keep the acquisition picture clean.
How often should I review MER?
Weekly, with decisions based on the four-week trend. Daily MER is dominated by noise from order timing, promotions and weekday effects.
How Glimmio handles this
Glimmio reconciles Meta and Google Ads spend against Shopify revenue in one place, so blended efficiency is a number you read rather than a spreadsheet you maintain.
Platform-reported figures stay labeled as platform-reported. Nothing is silently blended into a single flattering total, because the gap between the two is information worth keeping.
- Manual approval by default — nothing runs unattended
- New campaigns and ads are always created paused
- 7-day recovery window on eligible changes
- 48 permissions across 13 roles, scoped per client account
Go deeper on this
The product pages and setup guides that cover what this article describes.
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