Google Ads Conversions in GA4: Why the Numbers Differ

Two systems each count what they believe happened. The gap between them is not a bug to remove. It is a measurement to track, and the trend matters more than the size.

Google Ads conversions and GA4 key events differ because they count different things: Google Ads credits a conversion to an ad interaction under its own attribution settings, while GA4 counts key events across the whole property and assigns them to sessions using its own rules. A gap is expected. The useful move is to measure it monthly and watch for sudden changes.

The same logic explains why ad platform conversions never match your store. GA4 is another observer in the same room.

Six reasons the numbers differ

1. Scope. GA4 counts a key event whichever channel produced the session. Google Ads counts only conversions tied to its own ads. Comparing GA4's all-channel total to Google Ads is comparing a whole with a part.
2. Attribution rules. Google Ads attributes a conversion to the ad interaction according to the account's attribution setting. GA4 attributes a key event to the session's source and medium, and its reports can use different attribution models. The same purchase can be credited to different places.
3. Click versus event date. Google Ads can report a conversion against the date of the click that led to it; GA4 reports it on the date the event happened. A click on the 30th that converts on the 2nd is in a different month in each system.
4. Interactions Google Ads can count. Depending on settings, Google Ads can include view-through conversions or modeled conversions that GA4 will not show as a session from that ad.
5. Consent and blocking. If a visitor declines analytics cookies, GA4 may not record the session while Google Ads may still record the conversion through its own mechanism, or the reverse.
6. Different definitions of "the same" conversion. A purchase key event in GA4 and a purchase conversion action in Google Ads might fire on different pages or counting rules, such as one per click versus every purchase.

None of these means one system is wrong. They are different instruments.

A method that turns the gap into information

Compare like with like, then track the ratio.

1. Take Google Ads conversions by month for the conversion action that matches your key event.
2. Take GA4 key events by month, filtered to the Paid Search channel group.
3. Divide GA4 by Google Ads for each month. Use the summed monthly figures, not an average of daily ratios.

Illustrative example, not real data: if Google Ads reports 200 conversions in March and GA4 shows 150 paid search key events, the ratio is 0.75. If April is 210 and 158, the ratio is about 0.75 again. That stability is good news. If May is 220 and 90, the ratio has fallen to 0.41 and something changed in May: a tag, a consent banner, a redirect that strips parameters, or a change to which conversion action Google Ads counts.

Two caveats. The Paid Search group in GA4 also includes search ads from other networks if they are tagged as paid search, so the comparison is tidier if Google is most of your paid search. And untagged Google Ads traffic can land in other channels; auto-tagging should be on.

Which number to trust for which decision

• Comparing campaigns with each other: Google Ads conversions, since the same rules apply to all of them.
• Judging whether a total is believable: your store or CRM. The platforms both overclaim and underclaim in different ways.
• Understanding on-site behavior after the click: GA4, using engagement and landing page data.

See how to calculate ROAS by channel if you take conversion value into the same exercise.

Doing the comparison with Quiriz

Both Google connectors are in beta, read-only, refresh daily and are included in paid plans. With a Google Ads account and a GA4 property connected, the monthly comparison is a question. Google Ads conversions come from the Campaign performance dataset; GA4 key events come from Daily traffic, which has a channel column, so you can filter to Paid Search. Questions like:

• "By month, how many Google Ads conversions did we have, and how many key events did GA4 record for Paid Search?"
• "What is the ratio of GA4 paid search key events to Google Ads conversions each month?"
• "In which month did that ratio change the most?"

Google Ads conversions and GA4 key events are each defined once in Company Context and the ratio is computed from monthly sums. The answer shows the monthly table behind the ratio.

Diagnosing a sudden change in the ratio

When the ratio moves, work through the likely causes in order of how cheap they are to check. First, did the date range or time zone setting change in either system. Second, was a tag, a consent banner or a checkout page edited that week, since a broken GA4 purchase event leaves Google Ads untouched while GA4 drops. Third, did someone change which conversion action Google Ads counts, or switch the primary conversion goal. Fourth, did auto-tagging stay on, since traffic without the Google click identifier can fall into other channel groups and shrink the Paid Search count. Last, compare both against your store or CRM for the same weeks. Whichever of the two systems stayed in line with your own orders is the one that is still working.

Limits

• GA4 key events are one combined total. The connector does not split them by event name, so if you have several key events, the comparison is against all of them.
• GA4 data is by default channel group, not by campaign. You cannot match individual Google Ads campaigns to GA4 sessions from this data.
• Time zones can differ between the ad account and the property; each dataset uses its own account's time zone.
• Recent days in both systems can be restated, so the latest month is provisional.

Start with asking GA4 questions and asking Google Ads questions if you want each side first. For paid media workflows, see Quiriz for paid media.

Frequently asked questions