Every ad platform grades its own homework. Google Ads and Meta will both happily claim credit for the same sale, each using its own attribution window and its own rules. Add up the revenue each platform reports and it is not unusual for the total to exceed what actually landed in your ecommerce platform or CRM.
That is not a reason to distrust the platforms entirely. It is a reason to be clear about what their numbers are for.
Where the gap comes from
- Overlapping attribution. A customer who clicks a Meta ad on Monday and searches your brand name on Thursday can be counted as a conversion by both platforms.
- Branded search inflation. Brand campaigns often post the best ROAS in the account because they capture demand that already existed. Some of that revenue would have arrived anyway.
- View-through and modelled conversions. Useful signals for the algorithm, but weak evidence that the ad caused the sale.
- Tracking hygiene. Duplicate tags, purchase events firing on page reloads, test orders and refunds that never get deducted all quietly inflate reported results.
A more honest scorecard
Use platform ROAS for what it is good at: optimising within a channel. Comparing ad sets, creative and bidding strategies inside Meta, or campaigns inside Google Ads, is exactly what it is built for.
For decisions between channels, and for conversations with leadership, anchor on blended numbers instead:
- Marketing efficiency ratio (MER): total revenue divided by total ad spend, measured from your own backend.
- New customer acquisition cost: spend divided by genuinely new customers, not total orders.
- Brand and non-brand split: report them separately so strong brand results cannot mask weak prospecting.
- Monthly reconciliation: compare platform-reported conversions against backend orders and investigate any gap that suddenly widens.
Where volume allows, go one step further and test incrementality. Geo holdouts or planned budget pauses in one region show what a channel is really adding, rather than what it claims.
What changes when you measure this way
Budget moves towards the activity that is genuinely creating demand, rather than the campaigns best positioned to take credit for it. Brand spend usually gets trimmed, prospecting gets a fairer hearing, and reporting conversations stop being arguments about whose numbers are right.
If your platform dashboards look healthy but the business is not feeling it, the measurement is the first place to look. Get in touch if you would like a second set of eyes on yours.