Your Meta Ads dashboard says 6x ROAS. Your finance team says revenue is flat. Both are correct — and that’s the problem.
ROAS (Return on Ad Spend) is the most-cited metric in paid social and one of the most misleading. Here’s why.
What ROAS Actually Measures
ROAS = Revenue attributed to ads ÷ Ad spend.
Sounds straightforward. The problem is in the word “attributed.” Meta’s default attribution window credits a purchase to an ad if the user saw or clicked it within the last 7 days (click) or 1 day (view). That means:
- A customer who would have bought anyway after seeing your brand once gets attributed to the ad
- A customer who discovered you organically but was retargeted gets counted as an ad-driven sale
- A customer who bought via email after clicking an ad gets counted twice — once in Meta, once in your email platform
The result: platform ROAS consistently overstates actual ad-driven revenue by 30–80% depending on your attribution overlap.
The Metrics That Actually Matter
MER (Marketing Efficiency Ratio)
Total revenue ÷ total marketing spend. Includes all channels. Not manipulable by attribution settings. This is the number that tells you whether marketing is profitable as a whole.
Incrementality
The revenue you would not have generated without the ad. Measured through holdout tests — turn off ads for a segment of your audience and compare purchase rates. Uncomfortable to run. Essential to understand.
CAC by channel
Customer acquisition cost segmented by the channel that sourced the first touchpoint — not the last one that got the attribution credit.
What Good Looks Like
A well-run paid social operation tracks:
- Platform ROAS as a directional signal — is it going up or down over time?
- MER as the profitability anchor — are we efficient overall?
- Blended CAC against LTV as the growth viability check
- Incrementality tests quarterly to validate whether spend is actually driving revenue or just capturing it
The Practical Fix
Before your next budget review, pull your total revenue for the last 90 days and divide it by your total marketing spend. That’s your MER. Now compare it to your platform ROAS.
The gap between those two numbers is your attribution inflation. If it’s larger than 40%, you’re making budget decisions based on fiction.
Fix the measurement before you fix the spend.