What is MER? Meaning, Formula, and When to Trust It Over ROAS
Also known as: Marketing Efficiency Ratio, blended ROAS
Short answer
MER is the ratio of all your business revenue to all your marketing cost, regardless of which campaign claims the sale. A MER of 5 means every $1 of marketing cost sat alongside $5 of total revenue.
Formula
MER = Total Revenue / Total Marketing Cost
Example
This month revenue is $250,000. Marketing cost across every channel is $50,000. MER = 250,000 / 50,000 = 5.
Why this number exists
Every ad platform counts itself as the cause of a sale. When Meta, Google, and TikTok each claim the same sale, their claims add up to more than the sales you actually made.
MER cannot be gamed because it never asks who caused what. It simply divides total revenue by total cost.
Reading it next to ROAS
| What you see | What it means |
|---|---|
| ROAS up, MER up | Real growth |
| ROAS up, MER flat | Platform claims overlap |
| ROAS up, MER down | Budget rose without incremental results |
| ROAS down, MER flat | An attribution change, not a business change |
Common mistakes
- Using MER to decide which campaign to cut. MER does not separate campaigns.
- Leaving out non-ad marketing cost. Tools, content, and affiliate commission are marketing cost.
- Comparing MER across months with different seasons. A holiday month and an ordinary one are not comparable.
Frequently asked questions
- Why use MER when ROAS exists?
- ROAS depends on attribution, and attribution can be wrong or double-counted across platforms. MER uses figures nobody can argue with: total revenue and total cost. That makes it a useful sanity check on ROAS.
- What is the weakness of MER?
- MER will not tell you which campaign works. It only gives overall direction. Use MER for business-level decisions and ROAS or CPA for campaign-level ones.
- When do MER and ROAS disagree?
- If every platform reports rising ROAS while MER falls, the platforms are claiming the same sales. Trust MER, then inspect your deduplication and attribution windows.
Related terms
Your ad numbers are only as accurate as the data behind them
Konektor captures the Click ID and sends conversions that close on WhatsApp, over the phone, or in a shop back to the ad platform.