Meta says it drove 500 conversions, Google Ads claims 420, and GA4 shows 610 across both, and someone asks you which number is right. The honest answer is all of them and none of them, and reconciling the gap is a core analyst skill. Here is how to do it.

Why the numbers never match

The mismatch is not a bug; it is the inevitable result of each tool counting by its own rules. Ad platforms count conversions by the date of the ad click within their own attribution window, claim credit for their own channel, and add modeled conversions. GA4 counts by the date the event happened, under its own attribution model, across all channels. Different timing, different credit, different scope guarantees different totals.

List the specific differences

Before reconciling, name the reasons they diverge, because each is a separate adjustment:

  • Attribution model – platforms often use their own click-based or modeled logic; GA4 uses data-driven or last-click.
  • Attribution window – a platform's window and GA4's lookback rarely match.
  • Credit scope – each platform claims only its own conversions, so platforms overlap and double-claim the same sale.
  • Counting time – click date versus conversion date shifts conversions between days.
  • Modeling – platforms inject modeled conversions GA4 does not.

Align what you can

Reconciliation is about making a fair comparison, not forcing identical numbers. Where possible, align the attribution windows between the platform and GA4, compare the same date range on the same counting basis, and look at a single channel at a time rather than totals. Narrowing the variables is what turns a wild discrepancy into an explainable one.

Expect platforms to over-claim in total

The classic pattern is that the sum of platform-reported conversions exceeds reality, because Meta and Google each take full credit for sales the other also influenced. GA4, seeing all channels together, deduplicates that overlap and usually lands lower than the platforms combined. Understanding this makes GA4 the better source for cross-channel totals, while each platform remains useful for optimizing its own campaigns.

Reconcile to a source of truth

For revenue especially, neither GA4 nor the platforms is the final word; your backend or CRM is. Tie both back to actual orders:

  • Compare GA4 conversions and platform conversions against backend order counts for the period.
  • Use the backend total as the denominator, and treat platform and GA4 figures as different lenses on it.
  • Flag any source reporting more conversions than the business actually had, which signals double counting.

Document the expected gap

Reconciliation is not a one-time fix but an ongoing explanation, so write down the expected relationship. A short note saying platforms will over-claim, GA4 will dedupe lower, and the backend is truth turns every future why-do-these-differ question into a reference rather than a fire drill. The gap is permanent; your job is to make it understood, not to close it.

Turn it into a standing report

Reconciliation done once is wasted, because the numbers drift apart again next week. Build a simple recurring view that places platform conversions, GA4 conversions, and backend orders side by side for the same period, so the relationship between them is visible at a glance and a sudden divergence stands out immediately. When the comparison is a standing report rather than a fire drill, you catch a broken tag or a double-counting bug days after it appears, not a quarter later when someone finally questions the totals.

When three tools report three conversion numbers, all are right in their own frame and none is the single truth, and reconciling them is about fair comparison, not forced agreement. Name why they differ, align windows and scope where you can, expect platforms to over-claim, and anchor everything to your backend. Do that and the question of which number is right becomes a clear explanation instead of an argument no one can win.

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