Free calculator
MER calculator. The ad number your bank balance agrees with.
Enter total revenue and total ad spend across every channel to get your marketing efficiency ratio. Or work backwards: the revenue a target MER needs, the spend it allows, and the gross profit left after ads. Free, in any currency. We ask for a work email once, before the first result.
MER = total revenue ÷ total ad spend
Your result
4.00×
in total revenue for every 1 of ad spend
The maths
MER uses totals: every sale from every channel, against all ad spend in the same period. Swap in revenue that an ad platform reported and it stops being MER and becomes ROAS again.
Reading the number
What MER tells you that ROAS cannot.
No platform can claim the same sale twice
Each ad platform reports the sales it thinks it caused, and together they often claim more than you sold. MER skips attribution: total revenue over total ad spend. If it holds while spend goes up, that is a good sign the extra spend is paying its way, though sales, repeat buyers and seasonality move it too.
It hides which channel did the work
MER is a business number, not a campaign number. When it falls, you know something got less efficient, not what. Use ROAS and creative data to find the cause, and MER to decide whether to keep spending.
Set the target from your margin
At a 40% gross margin, ad spend eats all of the gross profit at a MER of 2.5. Above that, ads leave gross profit to pay for everything else. The Profit after ads tab shows how much.
FAQ
MER, answered.
What is MER in marketing?
MER stands for marketing efficiency ratio: total revenue divided by total ad spend over the same period, across every channel. A MER of 4 means the business made 4 in sales for every 1 it spent on ads. Some teams call it blended ROAS.
How do you calculate MER?
Divide total revenue by total ad spend for the same dates. MER = total revenue ÷ total ad spend. For 1,200,000 in revenue and 300,000 of ad spend, MER is 4.
What is the difference between MER and ROAS?
ROAS divides the revenue one platform credits to its ads by that platform's spend. MER divides all revenue by all ad spend. ROAS tells you which campaign to fund; MER tells you whether the whole budget is paying off.
What is a good MER?
One that leaves profit after your other costs. Start from break-even, 1 ÷ gross margin: at a 40% margin that is 2.5. You need to sit comfortably above break-even to cover fixed costs, so set the target from your own margin, not from another brand's benchmark.
Should MER include agency fees and software?
Pick one definition and keep it. Many ecommerce teams count paid media spend only; others count all marketing costs, including agency fees, production and tools. Adding those costs lowers the ratio and brings it closer to profit. Either works; switching between them from month to month does not.
What is new-customer MER?
Some teams divide revenue from first-time buyers only by ad spend, often called acquisition MER or aMER. It strips out repeat buyers who might have bought anyway, so it shows how well the ads win new customers. You need new and returning revenue split in your store data.
Why does MER fall when I raise spend?
The cheapest demand is bought first, so each extra unit of spend reaches people who were less ready to buy. A falling MER while you scale is normal. The question is whether gross profit after ads went up, which the Profit after ads tab shows.
MER says the budget worked. It cannot say which ads did it.
Marxx reads every ad in your account, tags it by hook, angle, format and offer, and rolls spend, CPA and ROAS up by those tags. When MER moves, you can see which kind of ad moved it.