Your Meta dashboard says 4.2x ROAS. Your Google dashboard says 5.1x. Your bank account says the business grew 6% last quarter. Somebody is lying, and it is not the bank account.
Platform ROAS is not a measurement; it is a claim, produced by the seller of the advertising, using rules the seller chose. Understanding exactly how the number is inflated is the first step toward metrics you can actually run a business on.
The Three Inflation Mechanisms
Platform ROAS overstates reality through three compounding mechanisms.
- Attribution windows: a purchase seven days after a click, or one day after merely seeing an ad, counts as ad-driven revenue. Loyal customers who would have bought anyway are swept in.
- View-through conversions: someone scrolled past your ad, bought later through search or email, and the platform claims the sale. In retargeting-heavy accounts, view-through can be a third or more of claimed revenue.
- Double counting across platforms: Meta and Google both claim the same purchase when a buyer touched both. Add platform numbers together and you are counting sales twice.
The Retargeting Illusion
Nowhere is the lie more flattering than retargeting. Your warmest audience, people already visiting your site and adding to cart, gets served cheap impressions right before they buy. The campaign reports a spectacular ROAS because it stands at the end of the checkout line taking credit for everyone who walks past.
Incrementality tests on retargeting are consistently humbling: holdout studies routinely show that a large share of retargeting-attributed revenue would have happened anyway. Retargeting has a real role, but its platform ROAS should be read as fiction with a basis in truth.
Retargeting stands at the end of the checkout line taking credit for everyone who walks past.
What to Track Instead
The fix is to anchor decisions in blended metrics that cannot be gamed by attribution rules, and use platform metrics only for relative comparisons.
- MER (marketing efficiency ratio): total revenue divided by total marketing spend. Crude, honest, ungameable.
- Blended CAC: total spend divided by total new customers. The number that decides whether growth is affordable.
- New-customer ROAS: strip out returning customers, who inflate every campaign they touch.
- Incrementality-adjusted returns: platform numbers discounted by what holdout tests reveal, channel by channel.
Using Platform ROAS Correctly
None of this means ignoring platform metrics. Within a single platform, under consistent settings, ROAS is a useful relative signal: this creative beats that one, this audience beats that one. The mistake is treating it as an absolute measure of business return, or comparing it across platforms with different attribution rules.
Run the account on platform signals. Run the business on blended truth. Teams that keep those two uses separate stop having the quarterly meeting where the dashboards say everything is winning and the P&L disagrees.