ROAS vs MER: Which Number Should a UAE Ecommerce Brand Actually Trust?
Platform-reported ROAS flatters you. MER does not. Here is what each number measures, why your ROAS hides COD refusals and returns, and how to report all three to a CEO without confusion.
What each number measures
ROAS vs MER is not a subtle debate. They measure different things, and the difference matters more in the UAE than in most markets because of how COD and returns distort the picture. ROAS — return on ad spend — is revenue attributed to a campaign divided by that campaign’s spend. It is reported by the ad platform (Meta, Google, TikTok) and is based on the platform’s own attribution model.
MER — marketing efficiency ratio — is total revenue divided by total marketing spend. It is not campaign-level. It is not attributed. It is a blunt, honest number: all the money that came in divided by all the marketing money that went out. You calculate it from your finance system, not from an ad dashboard.
The reason they diverge is attribution. Platforms take credit for revenue that multiple touchpoints contributed to. A customer who saw a Meta ad, clicked a Google ad, and then bought directly — both platforms may claim that revenue. Add up platform-reported revenue and it can exceed actual revenue. MER does not have this problem because it starts from actual revenue.
Why platform-reported ROAS flatters you
Platform ROAS is not lying, but it is optimistic. It uses last-click or data-driven attribution that tends to credit the platform for conversions it touched, even if the real decision was made earlier in the journey. It also counts revenue at the point of purchase — before returns, before COD refusals, before cancellations. The ROAS number on your dashboard is the best-case version of your performance.
This is not a conspiracy. It is how attribution works. But it means a brand that sees "ROAS of 4x" on Meta might be looking at a number that includes orders that will be returned, orders that will be refused at delivery, and revenue that Google also claimed. The real number — what the finance team sees — is lower.
For a deeper look at how to calculate what your campaigns actually produce, our guide on true ROI on performance marketing covers the gap between platform-reported and finance-confirmed numbers.
MER and contribution margin as the sanity check
MER is the sanity check. If your total revenue is AED 1 million and your total marketing spend is AED 200,000, your MER is 5. That is the number your CFO cares about because it reflects the actual relationship between marketing investment and revenue. It does not tell you which campaign drove which sale, but it tells you whether your marketing as a whole is paying for itself.
Pair MER with contribution margin — the profit left after product cost, shipping, COD fees, and returns. A MER of 5 with a 20% contribution margin means marketing is producing profitable growth. A MER of 5 with a 5% contribution margin means you are growing revenue but barely covering costs, and one bad month puts you underwater.
The combination — MER for overall efficiency, contribution margin for profitability — is what separates ecommerce brands that scale sustainably from brands that grow their top line while bleeding cash. For new brands building this from scratch, the performance marketing funnel guide covers how to set up the measurement infrastructure from day one.
The cost your ROAS never sees: COD refusals, returns and cancellations
In the UAE ecommerce market, COD is a significant portion of orders for many categories. COD refusals — where the customer ordered but refuses to accept delivery — are a cost that platform ROAS never sees. The platform counts the order as revenue. Your warehouse counts it as a returned shipment with shipping costs both ways. Your finance team counts it as zero revenue with real costs.
Returns and cancellations have the same effect. The ROAS number includes the original order value. It does not get adjusted when the order is returned or cancelled. For a brand with a 15% return rate and a 10% COD refusal rate, the gap between platform ROAS and real ROAS is enormous — the platform is counting revenue that does not exist.
This is why MER matters so much in this market. MER starts from real revenue — revenue after returns, after refusals, after cancellations. It does not flatter you. For more on how COD specifically affects your funnel economics, see our piece on COD and ecommerce marketing. The cost structure of COD is different from card-based ecommerce, and the metrics you trust need to account for that.
How to report all three to a CEO without confusing them
When you report to a CEO or a board, lead with MER and contribution margin. These are the numbers that tell the business whether marketing is profitable. "Our MER is 5 and our contribution margin is 22%" is a clear, honest statement.
Then use ROAS as a diagnostic, not a headline. "Meta reports 4x ROAS, Google reports 3.5x, and our MER is 5 — the gap is attribution overlap and COD refusals." This tells the CEO where the efficiency is coming from and why the platform numbers are higher than the real number.
Do not present platform ROAS as the primary metric. It sets an expectation that is not achievable in reality, and when the finance numbers do not match, you spend the next meeting explaining why. Lead with the truth — MER and margin — and use ROAS to explain the campaign-level story underneath it. That is how you build trust with the people who sign off on the budget.