The Number Doesn't Match — Now What?
Your Google Ads campaign shows 500 conversions this month. Google Analytics shows 320 conversions from Google / CPC. Your client wants to know why, and the answer "they measure differently" isn't going to satisfy anyone.
Understanding why these numbers diverge — and how to reconcile them — is a core competency for any digital marketing professional.
The Most Common Causes of Discrepancy
1. Different attribution models Google Ads defaults to data-driven attribution. Google Analytics GA4 uses last-click by default (though this is configurable). The same conversion counted under different models will produce different numbers.
2. Different lookback windows Google Ads conversions may use a 30-day or 90-day click lookback window. GA4 records the session date of the conversion, not the original click date. A conversion from a click 25 days ago appears in last month's Google Ads data but this month's GA4 data.
3. Cross-device and cross-browser gaps Google Ads can use signed-in Google data to attribute cross-device conversions. GA4 typically requires a user ID or cookies to connect sessions across devices. A conversion that Google Ads "sees" across devices may be invisible to GA4.
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4. Google Ads conversion actions vs. GA4 goals You may have more conversion actions configured in Google Ads than you have goals in GA4. Or the triggering conditions don't exactly match. "Purchase" in Google Ads might fire on any order confirmation, while "Purchase" in GA4 fires only on confirmed paid orders.
5. Spam and bot traffic GA4 attempts to filter bot traffic. Google Ads may count interactions that GA4 classifies as non-human, producing inflated click and conversion counts in Ads versus GA4.
How to Reconcile
Step 1: Agree on a primary source of truth. For most purposes, backend conversions (your actual database of orders, leads, or signups) are the most reliable. Everything else is an approximation.
Step 2: Standardize attribution. Use the same attribution model in both platforms, or note which model each is using when comparing.
Step 3: Align conversion actions. For each conversion you care about, verify the trigger is identical in both platforms.
Step 4: Present with context. In client reports, show conversions from your primary source (GA4 or backend) with a footnote explaining why Google Ads shows a different number.
Setting Client Expectations
"Google Ads and GA4 will always show slightly different conversion numbers — this is normal and expected due to differences in attribution methodology and device tracking. We use GA4 as our primary measurement source because it's consistent across all channels. Google Ads numbers are a useful signal for optimizing the campaigns, not the canonical conversion count."
