Google Ads vs GA4 Conversion Mismatch: Why and How to Fix It

You check Google Ads: 50 conversions. You check GA4: 35 conversions. Your actual CRM: 62 sales. None of the numbers match. What’s going on?

Here’s the uncomfortable truth: these numbers will never match perfectly. But understanding why helps you know which number to trust and when.

Why the Numbers Are Different

Different Attribution Models

Google Ads and GA4 use different attribution models by default:

Google Ads (2024 default): Data-driven attribution

Gives partial credit to multiple touchpoints
One conversion might count as 0.3 for one campaign and 0.7 for another
Optimized for Google’s ad ecosystem

GA4 (default): Data-driven attribution for conversions, last-click for acquisition

Different data-driven model than Ads
Can show fractional conversions in some reports
Optimized for understanding the full journey

Result: The same conversion can be “counted” differently in each platform.

Different Conversion Windows

Google Ads click conversion window: 30 days (default) Google Ads view-through window: 1 day (default) GA4 attribution window: 30 days for all channels

Someone who clicked an ad on Jan 1 and converted on Jan 25:

Google Ads: Counts the conversion (within 30-day window)
GA4: Counts the conversion (within 30-day window)

But view-through conversions? Google Ads counts them. GA4 (by default) doesn’t have view-through.

Different Counting Methods

Google Ads: Counts “every” conversion by default

1 user making 3 purchases = 3 conversions

GA4: Counts “one” conversion per session by default for most events

1 user making 3 purchases in one session = 1 conversion (unless configured otherwise)

Check your GA4 conversion counting method: Admin → Events → Your conversion → Counting method.

Different Data Sources

Google Ads knows:

Every click on your ads
Cross-device conversions (if user is signed into Google)
Modeled conversions (when real data isn’t available)

GA4 knows:

Every pageview where GA4 loaded
Events that fired correctly
Users who didn’t block tracking

These are different datasets that happen to overlap.

Blocked tracking affects GA4 more than Google Ads:

Ad blockers block GA4 more reliably than Google’s ad click tracking
Google can model some conversions from users who blocked GA4

This means Google Ads often shows MORE conversions than GA4.

How to Diagnose the Discrepancy

Step 1: Check Time Periods Match

Obvious but often missed:

Are both platforms set to the same date range?
Are both using the same timezone?
Google Ads uses the click date; GA4 uses conversion date

Step 2: Check Conversion Definitions

In Google Ads:

Tools & Settings → Conversions
Click on your conversion action
Note the settings: counting, attribution window, attribution model

In GA4:

Admin → Events → Click on the conversion event
Check counting method

These should match (or you should understand why they differ).

Step 3: Check Conversion Lag

Google Ads has a “Days to conversion” report:

Campaigns → Conversions
Segment by “Days to conversion”

If many conversions happen on day 7-30, you’ll see big discrepancies when comparing recent date ranges.

Step 4: Verify Linking

GA4 and Google Ads should be linked:

GA4 Admin → Product links → Google Ads links
Verify your account is connected
Check that conversions are being imported

If you’re using GA4 conversions in Google Ads, the numbers should be closer (though still not identical due to attribution differences).

Step 5: Check for Duplicate Conversion Actions

Common mistake: Having BOTH a Google Ads tag and a GA4 import for the same conversion.

In Google Ads → Conversions, you should have EITHER:

A Google Ads conversion tag, OR
An imported GA4 conversion

Not both. If both exist, you might be double-counting OR using different data sources for different campaigns.

Which Number Should You Trust?

For Google Ads Optimization: Trust Google Ads

Google’s bidding algorithms optimize using Google Ads conversion data. Even if the number is “wrong” compared to GA4, it’s what the algorithm sees. Changing your conversion source mid-campaign can reset learning.

For Understanding Full Journey: Trust GA4

GA4 sees more of the picture across all channels. If you want to understand how organic, social, email, and paid work together, use GA4.

For Actual Business Performance: Trust Your Backend

Neither Google Ads nor GA4 knows about:

Returns and refunds
Cancelled orders
Fraudulent transactions
Revenue from subscriptions

Your CRM/database is the source of truth for actual business outcomes.

Making the Numbers Closer

You can’t make them match perfectly, but you can reduce the gap:

1. Use the Same Attribution Model

Set both to the same model (data-driven or last-click) for easier comparison.

2. Import GA4 Conversions to Google Ads

Instead of running separate Google Ads conversion tags:

Set up conversions in GA4
Import them to Google Ads
This ensures same data source for both reporting views

3. Align Conversion Windows

Set the same conversion window in both platforms.

4. Use Enhanced Conversions

Enhanced conversions improve matching between what Google Ads sees and what your backend recorded, reducing modeled/estimated conversions.

5. Implement Server-Side Tracking

Server-side tracking (via GTM server container or Google Ads API) reduces the gap caused by ad blockers and client-side tracking issues.

The Acceptable Discrepancy Range

After proper configuration:

10-20% discrepancy: Normal and acceptable
20-30% discrepancy: Worth investigating but may be explainable
30%+ discrepancy: Something is likely misconfigured

If you’re seeing 50%+ differences, there’s a technical problem somewhere.

Still Can’t Reconcile the Numbers?

Conversion tracking discrepancies are one of the most common issues we diagnose. Get a free scan and we’ll identify whether your conversion tracking is properly configured across both platforms.