Google Ads credits a conversion to the ad that preceded it within its own attribution window, including view-through. GA4 credits the last channel it observed in the session. Google Ads therefore claims conversions GA4 assigns elsewhere, and the gap widens with longer windows and more display inventory.
What is each tool actually counting?
Google Ads counts conversions it believes its own ads caused, looking backwards over its attribution window. GA4 counts conversion events it recorded, attributed to whichever channel it saw most recently in that session.
Those are two different questions. One asks what the ads contributed; the other asks where the visit came from. A single purchase can honestly be one conversion in both and credited to different channels.
Where does most of the gap come from?
Three places, in roughly this order.
- View-through conversions, which Google Ads may count and GA4 will not.
- Cross-device journeys, which Google Ads can stitch through signed-in users and GA4 often cannot.
- Different windows, so the same purchase falls inside one lookback and outside the other.
Should the two ever be reconciled?
No, and trying is how reporting time disappears. They answer different questions, so a reconciled number would have to abandon one definition, at which point it is no longer either tool's figure.
Report both, labelled by source, and be explicit about which one the decision is being made on. Consistency over time matters far more than agreement between tools.
Which one should a client see?
Whichever is being used to make the decision, with the other available. For budget decisions inside the ad platform, the platform's own number is the one the bidding responds to.
For revenue conversations, an analytics figure is usually closer to what finance recognises. Saying that plainly is better than being asked later why two documents disagree.
Frequently asked questions
- Is one of them wrong?
- Neither, under its own definition. What would be wrong is presenting either as the total truth, or mixing the two inside one table.
- Can I make GA4 match Google Ads?
- Not reliably. You can align the windows and import conversions, which narrows the gap, but the models differ in ways configuration cannot remove.
- Which should be in a monthly report?
- Both, in separate labelled columns. A single unexplained number invites the one question you cannot answer well.