Why don't GA4 and my ad platform conversion numbers match?
They count different things with different windows. Here is how to reconcile them.
GA4 and your ad platform are counting different actions, on different dates, under different attribution rules, so they will never match exactly. A steady gap is normal. A sudden gap is a bug.
If the two ever matched perfectly, we would go looking for the double count. The useful question is not why they differ, it is whether the difference is explained by method or by a broken tag.
The four reasons the numbers differ
- Click date versus conversion date. Google's help documentation on data discrepancies states that Google Ads reports conversions against the date and time of the click that led to the action, not the date of the action itself. GA4 records it on the day it actually happened. Click Monday, convert Friday, and the two reports file that conversion in different weeks.
- Different attribution models. Google Ads runs data-driven attribution by default and only credits its own clicks. GA4 spreads credit across paid and organic channels, and offers data-driven, paid and organic last click, and Google paid channels last click. Google retired the first click, linear, time decay and position based models in GA4 in November 2023.
- Different windows. A Google Ads conversion window is configurable from 1 to 90 days and defaults to 30. Google's attribution settings documentation puts the GA4 lookback window at 90 days by default for most key events and 30 days for acquisition events.
- Modeling and consent. Ad platforms report modeled conversions to fill the gaps left by consent choices, blockers and cross device journeys. GA4 models too, on a different basis. Meta self-attributes inside its own Ads Manager and will almost always claim more credit than GA4 gives it.
Counting rules matter too
Google Ads lets you count every conversion or only one per click. GA4 counts events. A form that fires its event twice reads as two in one system and one in the other. Check that setting before you chase anything else.
Which number should you run the business on
None of them alone. Use the ad platform number to feed bidding, because that is the data the algorithm actually optimizes against. Use GA4 to understand behavior on the site. Use your CRM to count revenue, because it is the only system that knows which leads were real. When the three disagree on scale but agree on direction, you are fine.
When the gap is a real problem
A stable percentage gap is method. Start worrying when one platform drops to zero, when the gap changes suddenly right after a site release, or when GA4 shows sessions from a campaign with no matching conversions at all. Those are tagging failures. Fixing them is part of our data and analytics work.
Related: What is conversion tracking and why does it break?, What is multi-channel attribution and which model should you use?, How do you track leads and conversions from paid campaigns?, Do you provide monthly reporting for paid campaigns?