BigQuery Google Ads Data Transfer - Conversion Data Discrepancies

[simplesix]

Certain tables in our BigQuery data transfer for Google Ads exactly match the conversion data reported in the Google Ads UI (for instance, the ads_adCrossDeviceConversionStats table). However, other tables do not and are wildly off. As an example, the ads_AdConversionStats table only reports conversions for 1 non-skippable in-stream video ad but fails to include several other skippable ads in the same campaign, all of which report various conversion actions within the Google Ads UI. I've run backfills and the data does not change. Any ideas on what is going on here?

[Snoshone07]

Hi @simplesix thanks for sharing your case — honestly, it’s more common than it seems when working with Google Ads automatic exports to BigQuery. Here are a few key points that could explain the discrepancy:

Possible reasons:

The ads_AdConversionStats table has extra filters

This table often excludes conversions that don’t meet specific criteria (for example, it may only show direct ad conversions, not multi-touch or post-view attributions).

Campaign type or ad format

Formats like skippable in-stream ads or responsive video ads might not register conversions directly if the attribution model or user interaction doesn’t qualify it as a direct conversion.

Attribution models
In the Google Ads UI, you might see conversions under models like Data-Driven Attribution (DDA), whereas the BigQuery export often reflects Last Click or stricter configurations.

Cross-device data
Some conversions you see in the UI are cross-device and appear in the ads_adCrossDeviceConversionStats table — but they might not be reflected across other tables.

Reporting latency
Sometimes conversions show up in the Google Ads UI first but take longer to appear in BigQuery due to attribution delays.

Bonus tip:

If you want greater control , like consolidating all your Google Ads conversion events into a cleaner, unified flow into BigQuery without depending on how Google splits the data across tables — you could look into using an external platform like Windsor.ai. It lets you pull Google Ads data at the event or conversion level, and you can also customize exactly which fields to fetch depending on your reporting needs.

Hope this helps!