MER / Blended ROAS

You are staring at three dashboards that all say different things. Meta says it made you 4x, Google says 5x, and yet your bank balance grew by less than either number would suggest. MER is the number that settles the argument. It is your total sales divided by your total ad spend across every channel put together, one honest figure for the whole business, instead of the score each ad platform hands itself.

The formula is as plain as it sounds. You take every rupee of sales you made in a period and divide it by every rupee you spent on ads in that same period. Say you did 300,000 in total sales last month and you spent 100,000 across Meta, Google and everything else combined. That is 300,000 divided by 100,000, which is a 3x MER. Every rupee you put into ads sat next to three rupees of sales.

Now put in your own two numbers. Take your total sales for last month and your total ad spend for last month, the full spend across all platforms, and see what ratio falls out.

The reason this matters is how platform ROAS is measured. Each platform grades its own homework. Meta counts a sale as its own if the buyer so much as saw the ad, and Google does the same, so when you run both at once they can each take credit for the very same order. Add those numbers up and you get a total that never landed in your account. MER cannot double-count, because it starts from your real total sales and your real total spend, so it sits much closer to what your bank actually sees.

Here is the catch. MER tells you the health of the whole picture, not which channel did the work. A 3x MER does not tell you whether Meta carried the month or Google did, and it will not tell you which campaign to cut. Use MER as your top-level pulse check on the business, and use the platform numbers, with a pinch of salt, to steer the day to day.

Platform ROAS tells you a story. MER tells you the truth.