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Google ads vs GA4 revenue number
Posted by on August 25, 2025 at 1:08 amI have a confusion. So we have two conversion setup in google ads. 1) GTM setting – primary 2) GA4 setting – secondary.
We use GA4 for our reporting. So when reporting I usually see the conversion value that I see inside google ads is inflated than the actual revenue that I’m seeing inside GA4.
If it’s for bidding purposes – I have to calculate my CAC and other high level KPI based on GA4 number because that’s what is closer to the actual revenue reflected backend.
Should I use the existing setup GTM- primary and GA4 secondary or should I change GA4 as primary so Gads and GA4 show same number.
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1 Reply
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Use the GTM setup as primary so Google Ads has consistent data for bidding.
GA4 should remain secondary, since it’s the closest match to actual backend revenue.
For reporting, CAC, and ROAS, rely on GA4 numbers instead of Ads—-Again this is due to the closeness to actual revenue numbers.
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You should correct gtm conv as well. The thing is the more close to actual conversion value you will get good results in automated biddings
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Yeah, that mismatch drives everyone a bit crazy. Ads always want to take more credit than GA4 shows. If GA4 is closer to your backend numbers, stick with that for real business KPIs. Let Ads do its thing for optimization, but don’t base finances on it
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The difference you’re seeing is normal, because Google Ads (via GTM tracking) and GA4 don’t measure conversions the same way:
**Google Ads (GTM tag as primary):** Uses last Google Ads click attribution (it gives full credit to the last ad click). Can include modeled conversions (like cross-device) that GA4 may not show.
**GA4 (set as secondary):** Uses data-driven attribution across all channels, not just Google Ads.
Why they don’t match: Different attribution windows, attribution models, and counting methods. Ads = ad-centric, GA4 = site/business-centric.
**Best practice:**
Keep your GTM conversion as the primary in Google Ads. That way bidding uses the signal Google expects (fast, Ads-optimized, consistent).
Use GA4 as secondary for reporting/comparison, and rely on GA4/backend numbers to calculate CAC, ROAS, etc. for business decisions.
So: stick with GTM as primary, GA4 as secondary.
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