What Is MER?
MER, or marketing efficiency ratio, is your total revenue divided by your total marketing spend over the same period. Bring in $500,000 in a month while spending $125,000 on marketing, and your MER is 4.0.
It's sometimes called blended ROAS or media efficiency ratio. The idea is the same: one number for the whole business, not one platform's view of it.
MER doesn't care which ad got the credit. It counts every sale, from every channel, against every dollar you spent to get them. That's what makes it useful, and it's also what makes it blunt.
How to Calculate MER
MER = total revenue ÷ total marketing spend
Both sides need clear rules, or the number drifts from month to month.
Revenue. Most brands use net sales: revenue after discounts and returns, before tax and shipping charged to the customer. Pick one definition and keep it.
Marketing spend. At a minimum, this is all paid media: Meta, Google, TikTok, CTV and anything else you buy. Some brands also add agency fees, creative production, influencer payments and affiliate commissions. Including them gives a truer number. Leaving them out makes it easier to compare to platform ROAS. Either works if you're consistent.
Time period. Weekly is usually too noisy. Monthly is the most common. Use the same window for revenue and spend.
Here's a made-up month for a brand that sells online and on Amazon:
| Amount | |
|---|---|
| Meta spend | $80,000 |
| Google spend | $30,000 |
| Other paid media | $15,000 |
| Total marketing spend | $125,000 |
| Shopify net sales | $380,000 |
| Amazon sales | $120,000 |
| Total revenue | $500,000 |
| MER | 4.0 |
Notice what's in the revenue line: Amazon sales, repeat orders from email, people who searched the brand name after seeing an ad. None of that has to be traced back to an ad. It's all in.
MER vs. ROAS
ROAS is revenue a platform attributes to its ads, divided by spend on that platform. MER is all revenue divided by all marketing spend. They answer different questions.
| ROAS | MER | |
|---|---|---|
| Revenue counted | Sales the platform attributes to its ads | Every sale the business made |
| Spend counted | One platform, campaign or ad | All marketing spend |
| Answers | Which ads and campaigns are working? | Is marketing as a whole paying off? |
| Depends on attribution | Yes | No |
| Sees retail and Amazon sales | No | Yes |
| Good for daily decisions | Yes | No |
| Who reports it | Ads Manager and other platforms | You, from your own books |
The two numbers almost never match. If you add up ROAS from every platform, you can end up with more revenue than you actually made, because more than one platform claims credit for the same order. Meta's number also depends on the attribution setting you choose. MER sidesteps all of that.
The trade-off is that MER can't tell you which ad, campaign or channel did the work. You still need ROAS for that.
So use both. ROAS for running the account day to day. MER for checking that the account is actually growing the business.
What Is a Good MER?
A good MER is one above your break-even point, and the math works just like break-even ROAS:
Break-even MER = 1 ÷ margin
At a 50% margin, you break even at an MER of 2.0. At a 40% margin, 2.5.
The margin you use should cover what each order really costs: product, shipping, payment fees and returns. If you've counted agency fees and production in your marketing spend, don't count them again in your costs.
| Margin after product, shipping and fees | Break-even MER |
|---|---|
| 30% | 3.33 |
| 40% | 2.50 |
| 50% | 2.00 |
| 60% | 1.67 |
| 70% | 1.43 |
Break-even only covers marketing. To find a target, add the profit you want to keep.
Target MER = 1 ÷ (margin − profit you want)
A brand with a 50% margin that wants 15% of revenue left after marketing needs an MER of about 2.86. Our ROAS calculator does the same math if you enter total spend and total revenue.
Two things change what a good number looks like.
Repeat customers. If most of your revenue comes from people who already bought, MER can look healthy while new customer growth stalls. Old customers are paying for the ads.
Growth stage. A brand pushing for new customers will usually run a lower MER than one coasting on its base. That's fine if new customers are worth it over time.
New Customer MER
Because MER counts repeat orders, a lot of brands also track a second version:
New customer MER = revenue from first orders ÷ total marketing spend
Some call this acquisition MER. It's a harder test. Repeat orders from email and subscriptions can't prop it up, so it shows whether your marketing is still finding new buyers.
If MER is flat and new customer MER is falling, you're leaning harder on your existing customers each month. One common cause is creative: ads that keep reaching the same people.
How to Use MER With Meta Ads
When Meta is a big share of your marketing budget, MER is a good check on whether Meta's numbers hold up.
Watch MER when you change Meta spend
The cleanest read comes from changing one thing at a time. If you raise Meta spend by 20% and total revenue climbs with it, the extra spend is working, whatever ROAS says. If MER drops sharply and revenue barely moves, Meta was taking credit for sales that would have happened anyway.
The reverse works too. Cut a chunk of Meta spend for a few weeks and watch total sales. If they hold, those ads weren't doing much. If they fall, the ads were doing more than Ads Manager said.
Don't judge ads on MER
MER is too blunt to pick winning ads. A new video that brings in new customers and a sale static that mostly reaches returning ones both feed the same total. Use ad-level numbers like cost per purchase to judge ads, and MER to judge the account.
Compare like with like
MER moves with the calendar. Across the consumer brands in our Black Friday data, ROAS was 82% higher on Black Friday 2025 than in October and 27% lower in the second week of December. Numbers that move that much with the season can't be read month to month. Compare a month to the same month last year, not to the one before it.
Test lift when the stakes are high
MER shows what happened to the whole business. It can't prove the ads caused it, since prices, launches, press and the season all move revenue too. A holdout test can. Meta's own lift tests split a sample of people at random into a test group and a holdout group, then measure the difference between them. That's slower and needs real budget, so it's worth it for big decisions, not routine ones.
Why MER Drops (And What to Check)
When MER slides, go through these in order:
- Spend went up. More spend usually means a lower MER, because each extra dollar reaches people less likely to buy. That can still mean more profit in total. Check the dollars left over, not just the ratio.
- Prices or margins changed. A discount lifts revenue but can cut profit. A price increase can do the opposite.
- Repeat revenue fell. Look at new customer MER to see if the drop is coming from new or returning customers.
- The ads are tired. In our data, the top ads kept only 29% of their spend three months later. When the account runs on a few old winners, cost per purchase creeps up and MER follows.
- Conversion rate dropped. Across 765 ads from 18 brands, conversion rate after the click explained about 85% of the difference in cost per purchase between a brand's ads. Ads that set the right expectations before the click convert better.
For more numbers, see our Meta Ads Statistics hub.
When MER Doesn't Fit
MER works best for brands that sell directly, with most marketing in paid channels. It's harder to use when:
- Your sales cycle is long. In B2B or high-ticket sales, this month's revenue came from marketing months ago.
- You're very small. A few large orders swing the number around.
- Paid media is a small part of your marketing. If most growth comes from wholesale deals or PR, MER mostly measures those.
In those cases, track spend against leads, trials or pipeline instead, and give it a longer window.
How We Help Brands Improve MER at Biddyco
We're a creative agency for Meta ads. We don't control your pricing or your other channels, but the ads are often the biggest lever on what Meta spend brings in. We make UGC, motion, static and hybrid ads for brands spending $100K to $5M a month, built to bring in new buyers, not just reach the ones you already have.
Our US-based senior team works across 100+ accounts and $20M+ in monthly spend. New files land every 2 to 4 weeks, and we aim for one round of feedback.
If MER is sliding and your ads are the likely reason, talk to us.
FAQ
What does MER stand for in marketing?
MER stands for marketing efficiency ratio. Some people say media efficiency ratio. Both mean total revenue divided by total marketing spend.
How do you calculate MER?
Divide total revenue by total marketing spend for the same period. $300,000 in revenue on $100,000 of marketing spend is an MER of 3.0.
Is MER the same as blended ROAS?
Mostly, yes. Both divide total revenue by total spend across channels. Some brands count only paid media in blended ROAS and add fees and production costs to MER, so check how a number was built before you compare it.
What is a good MER for ecommerce?
Any MER above 1 divided by your margin. At a 50% margin that's 2.0, and at a 40% margin it's 2.5. Your target should be higher, depending on the profit you want and how much your customers buy again.
Is MER better than ROAS?
Neither is better. They answer different questions. ROAS tells you which ads and campaigns are working inside one platform. MER tells you whether all of your marketing is paying off. Use ROAS to run the account and MER to check it.
Why is my MER lower than my Meta ROAS?
MER counts all marketing spend, not just Meta. And Meta's ROAS can include sales that other channels also claim, or that would have happened anyway. If MER is much lower than Meta ROAS, look at your other channels and at how much of Meta's reported revenue is new.
