ROAS vs MER: What's the Difference?
ROAS measures the revenue attributed to advertising relative to ad spend. MER measures total store revenue relative to total advertising spend. ROAS helps evaluate campaigns and channels; MER gives a blended view of advertising efficiency across the business.
ROAS vs MER at a glance
| ROAS | MER | |
|---|---|---|
| Revenue | Attributed revenue | Total store revenue |
| Spend | Ad/platform spend | Total ad spend |
| Best for | Campaign/channel efficiency | Overall marketing efficiency |
| Attribution dependent | Yes | Much less |
| Measures profit | No | No |
What is ROAS?
ROAS = attributed advertising revenue ÷ advertising spend
With €10,000 of Meta spend and €35,000 of Meta-attributed revenue, ROAS is 3.5×.
Platform ROAS depends on the platform's attribution rules and on the purchase value your store sends it. Attributed revenue is revenue the platform claims credit for within its attribution window — not revenue that is guaranteed to be incremental. Two platforms can each claim the same order.
What is MER?
MER = total store revenue ÷ total advertising spend
With €100,000 of store revenue and €25,000 of total advertising spend, MER is 4.0×.
MER (marketing efficiency ratio, sometimes called blended ROAS) is useful because it avoids assigning every sale to an individual advertising platform. It answers one question: for every euro of advertising, how much revenue did the whole store generate?
ROAS vs MER example
| Input | Amount |
|---|---|
| Store revenue | €100,000 |
| Meta spend | €15,000 |
| Google spend | €10,000 |
| Total ad spend | €25,000 |
| Meta attributed revenue | €45,000 |
| Google attributed revenue | €35,000 |
| Metric | Result |
|---|---|
| Meta ROAS | 3.0× |
| Google ROAS | 3.5× |
| MER | 4.0× |
Meta and Google together claim €80,000 of revenue, while the store actually made €100,000. The two platforms measure independently and both can count the same order, so adding attributed revenue together overstates results — and it ignores organic, email and repeat revenue that would exist without those campaigns. MER compares the revenue the store really recorded with the money really spent.
When should you use ROAS?
- comparing campaigns against each other
- channel optimisation
- creative and ad-set decisions
- platform-level efficiency over time
When should you use MER?
- blended marketing efficiency
- business-level advertising trends
- reducing dependence on platform attribution
- understanding total revenue relative to total acquisition spend
Why neither ROAS nor MER tells you your profit
Both metrics stop at revenue. Neither accounts for COGS, shipping, packaging, payment fees, refunds or other variable costs — and neither accounts for fixed costs at all.
Two stores can both run at a 3.0× MER and end the month in completely different places. If one keeps 55% of net revenue after variable costs and the other keeps 30%, the first is comfortably profitable at that MER and the second is losing money on every order.
Advertising efficiency tells you how efficiently you generated revenue. Contribution profit tells you how much remained after the costs required to generate and fulfil those sales. Work out the MER or ROAS your own economics require with the Break-even ROAS Calculator, or see what a full period actually left you with using the Ecommerce Profit Calculator.
Find the efficiency your margins actually require.
A store like the worked example in our calculator keeps €34.15 per order before advertising, which sets its break-even at 1.91× on net revenue. Enter your own costs to get yours.
Break-even ROAS CalculatorFrequently asked questions
- Is MER better than ROAS?
- Neither is better; they answer different questions. ROAS evaluates a campaign, ad set or channel using attributed revenue. MER evaluates the whole business using total store revenue and total advertising spend, so it does not depend on platform attribution.
- What is a good MER?
- It depends entirely on your contribution margin before advertising. A store that keeps 50% of net revenue after product, fulfilment and payment costs breaks even around a 2.0× MER; a store keeping 25% needs 4.0×. Calculate your own break-even instead of copying a benchmark.
- Can I add up ROAS from Meta and Google?
- No. Each platform counts a conversion it believes it influenced, so the same order can appear in both. Summing attributed revenue usually exceeds actual store revenue. Use MER when you want a total-business view.
- Does MER include organic and repeat revenue?
- Yes. MER uses total store revenue, which includes organic, email, referral and repeat purchases. That is why MER improves when retention improves, even if paid performance is flat.
- Should MER use gross or net revenue?
- Use the same revenue definition consistently. ProfitSimple uses net revenue — gross sales minus discounts, refunds and VAT — because VAT is never yours. If you use VAT-inclusive revenue, your MER will look higher than the profitability-correct figure.
Revenue efficiency isn't the same as profit.
Connect Shopify and see what your store actually kept after product, fulfilment, payment and advertising costs.
Connect ShopifyRelated calculators
- Break-even ROAS Calculator — the ROAS you need before ads become profitable
- Ecommerce Profit Calculator — your store's contribution profit for a period
- All ecommerce profitability guides