What is the marketing efficiency ratio (MER)?
The marketing efficiency ratio, or MER, is your total store revenue divided by your total ad spend over the same period. If your store took in $40,000 in a month and you spent $10,000 on ads across every network, your MER is 4.0x: each $1 of advertising went with $4 of revenue.
You will also see it called blended ROAS or total ROAS. Some teams put all marketing costs in the denominator, such as agency fees, creator payments and tools, instead of ad spend alone. Both versions are in use, so write down which one you track and keep it the same from month to month.
MER looks at the business from the store's side. The revenue comes from your own orders, so an order counts once even when Meta and Google Ads both claim it. That makes MER a useful reality check on the ROAS each ad platform reports.
The marketing efficiency ratio formula, with an example
MER = total store revenue ÷ total ad spend. Use the same dates, the same time zone and the same currency on both sides.
Illustrative example, not a customer result: a store has $40,000 of revenue in a month. It spent $6,000 on Meta, $3,500 on Google Ads and $500 on TikTok, $10,000 in all. Its MER is $40,000 ÷ $10,000 = 4.0x.
Now add up what the platforms report for the same month. Meta credits $24,000 of purchase value to its ads, Google Ads $18,000 and TikTok $3,000. Together they claim $45,000, more than the store's entire revenue, which also includes orders from email, organic search and direct visits. The overlap comes from each network crediting purchases under its own attribution settings. MER avoids it because it starts from the orders.
The inverse of MER, ad spend ÷ revenue, is the share of revenue that went to ads: 25% in this example.
| Report | Revenue counted | Ad spend | Ratio |
|---|---|---|---|
| Meta Ads Manager | $24,000 | $6,000 | 4.0x |
| Google Ads | $18,000 | $3,500 | 5.1x |
| TikTok Ads Manager | $3,000 | $500 | 6.0x |
| The three platforms added up | $45,000 | $10,000 | 4.5x |
| Store revenue (MER) | $40,000 | $10,000 | 4.0x |
MER vs ROAS vs blended ROAS
ROAS is usually measured per campaign or per network, with the revenue that ad platform credits to its own ads. MER is measured for the whole store, with every order. Blended ROAS is often a second name for MER, but some reports use it for the platforms' credited revenue added up and divided by total spend, which is the 4.5x above. Check which revenue a blended number uses before you compare it with anything.
| Ratio | Revenue | Spend | Question it answers |
|---|---|---|---|
| ROAS | Revenue the ad platform credits to a campaign or network | That campaign's or network's ad spend | How does this campaign look to the platform that ran it? |
| Blended ROAS | Usually all store revenue; sometimes the revenue the platforms credit, added up | All ad spend | Depends on the definition, so check it first |
| MER | All store revenue, from every channel, each order once | All ad spend, or all marketing costs if you define it that way | How much revenue did the store make per unit of ad spend? |
| POAS | Profit before ad spend | Ad spend | How much profit before advertising does each unit of ad spend leave? |
MER vs POAS: revenue efficiency is not profit
MER is a revenue ratio. Two stores with the same MER can end the month very differently, because what matters is how much of each order is left after the costs of selling it.
POAS, profit on ad spend, divides profit before ad spend by ad spend. In WeProfit, profit before ad spend is revenue minus refunds, taxes (sales tax or VAT), product costs, payment fees and shipping. The two ratios are linked: store-wide POAS = margin before ad spend × MER.
Take the $40,000 store with its 4.0x MER. With a 40% margin before ad spend, it keeps $16,000 before ads, its POAS is 1.6x and $6,000 remains after the $10,000 of ad spend. With a 20% margin, it keeps $8,000, its POAS is 0.8x and the month ends $2,000 down. The MER is the same in both cases.
That is why the MER you need depends on your margin, just like break-even ROAS: break-even MER = 1 ÷ margin before ad spend, which is 2.5x at a 40% margin and 5.0x at 20%.
| Measure | Store A | Store B |
|---|---|---|
| Revenue | $40,000 | $40,000 |
| Ad spend | $10,000 | $10,000 |
| MER | 4.0x | 4.0x |
| Margin before ad spend | 40% | 20% |
| Profit before ad spend | $16,000 | $8,000 |
| POAS | 1.6x | 0.8x |
| Profit after ad spend | $6,000 | −$2,000 |
| Break-even MER | 2.5x | 5.0x |
Where the MER inputs come from
Take revenue from your store's orders, not from the ad platforms. Decide whether you use revenue before or after refunds, and with or without sales tax or VAT, and keep that choice. Take ad spend from every network you paid in the period, in one currency.
In WeProfit, revenue is what customers paid for the store's orders: after discounts, with the shipping charged and the sales tax or VAT included, before refunds, from every channel. Cancelled orders are left out. Orders count on the day they were placed in the store's time zone, and ad spend on the day each ad platform reports it.
Spend from connected Meta, Google Ads and TikTok ad accounts syncs every hour and re-reads the last 3 days, because platforms restate them; a newly connected ad account brings in its last 30 days. For any network, you can also add spend under Profit > Ad spend, as manual entries or as a daily schedule that books itself every day until you change it, or push it through the developer API. Spend in another currency is converted into the store currency at the day's reference rate.
A manual entry for the same day, network and campaign takes priority over synced or scheduled amounts. If you keep manual or scheduled entries for a network that also has a connected ad account, the dashboard warns that the spend can count twice, because the account imports the same days as separate campaign rows.
Common MER mistakes
Most bad MER readings come from the inputs, not the formula. Watch for these:
- Platform revenue instead of store revenue. Adding up the revenue the ad platforms report gives a blended platform ROAS, not MER, and it counts shared orders more than once.
- Missing spend. Leaving out a network, an agency invoice you decided to include or a few days of spend makes MER look better than it is.
- Mismatched days or currencies. Revenue counted in your store's time zone and spend counted in an ad account's time zone, or amounts in two currencies, do not divide cleanly.
- A moving definition. Switching between ad spend and all marketing costs, or between revenue before and after refunds, breaks the trend line.
- One-day readings. Daily MER jumps with every big order and every spend change. Compare weeks or months.
How WeProfit shows MER
WeProfit does not label any number MER. The store-wide ratio sits in the breakdown of the POAS card on the Overview: hover How POAS is computed and read ROAS (revenue / spend). It divides all revenue of the selected days by all ad spend of those days, which is the MER formula.
Its revenue is every non-cancelled order placed on those days in the store's time zone, from every channel, including orders imported from before you installed WeProfit, and before refunds. Its spend is every spend entry of those days for every network: synced, scheduled, manual and API.
POAS is the card's headline number, so the store-wide revenue ratio and the profit ratio sit together. In the multi-store Overview, each store's totals are converted into one display currency at daily rates before POAS and ROAS are worked out.
What MER cannot tell you
MER is a good first number for the whole business and a poor last one. It cannot tell you:
- Which campaign worked. MER blends every channel. For campaign answers, look at revenue, ad spend, POAS and break-even per channel and campaign, which WeProfit shows on the Attribution page under Profit by channel & campaign.
- Whether you made money. MER leaves out product costs, refunds, shipping and fees: a 4.0x MER is a profit at a 40% margin before ad spend and a loss at 20%.
- Why it moved. Organic demand, seasonality, a price change or a large email send can raise or lower revenue with no change in ads, and MER moves with them.
- When the revenue arrives. Spend on one day and the orders it brings in can land on different days, so a single day's MER is noisy. Weekly or monthly MER is easier to read.
- What a new customer is worth. A first order counts once, in the period it was placed. Repeat purchases from the same customers show up later, in other periods.
- Whether the ads caused the sales. MER puts revenue and spend side by side; it does not measure how many orders the ads caused.