Why Google Ads and GA4 never agree on conversions

Open Google Ads and it says your campaigns brought 40 conversions last month. Open Google Analytics 4 for the same month and the same campaigns, and it says 31. Or 52. Both come from Google, both measure your site, and they almost never agree.

Usually neither is broken. The two products answer different questions, count on different days and give credit by different rules. Once you know the differences, the gap stops being worrying and starts being useful — and you know which number to use for which decision.

1. They put the conversion on different days

Google Ads reports a conversion on the date of the ad click that led to it. GA4 reports it on the date the conversion happened.

Someone clicks your ad on 28 September and buys on 3 October. Google Ads counts that sale in September; GA4 counts it in October. Over a month, sales made a few days after the click move between the two months, and the last days of any period look different in each product. In Google Ads the most recent days also keep rising for a while, as people who clicked recently go on to convert.

2. Google Ads only sees its own clicks

Google Ads gives credit for a conversion to Google Ads clicks, and nothing else. GA4 sees every way people reach you — search, email, social, other sites — and decides which of them gets the credit.

Someone clicks your ad on Monday, leaves, and on Thursday clicks a link in your newsletter and buys. In Google Ads that is a conversion for the ad. In GA4, depending on its attribution settings, the credit can go to the email, be shared between the two, or go to the ad. Google Ads is not inflating anything: from where it sits, its click did lead to a sale. It just cannot see the email.

This is the biggest source of the gap on most accounts, and it usually makes Google Ads show more conversions for your campaigns than GA4 credits them with.

3. The conversion window

Google Ads counts a conversion only if it happens within the conversion action's window after the click — 30 days by default, adjustable per action. A sale 45 days after the click is not a Google Ads conversion at all, but GA4 still records it and credits it to whichever channel its rules choose.

4. They may not be counting the same thing

• Which actions count. The Conversions column in Google Ads includes only the conversion actions set to be included in it (the primary ones). If yours includes a newsletter sign-up as well as purchases, it is counting more than GA4's purchase report.
• Every or one. Each Google Ads conversion action counts either every conversion after a click or only one. Set to one, three purchases after one click count once; GA4 records three.
• Two tags. If Google Ads uses its own conversion tag while GA4 has its own event, they are two separate measurements of the same thing, and each can fire where the other does not.
• Estimated conversions. Google Ads can include conversions it models rather than observes — for example across devices, or for people who declined cookies. GA4 has modelling of its own, applied differently.

5. Smaller things that add up

• Time zones. Each account has its own. If Google Ads runs on one and GA4 on another, the edges of every day differ.
• Linking and tagging. GA4 knows a visit came from Google Ads through the link between the two accounts and auto-tagging (the gclid on the click). If the accounts are not linked, or something on the site strips the parameter, GA4 files those visits elsewhere and your campaigns look worse in GA4 than they are.
• Revenue. Google Ads reports the conversion value it was sent; GA4 reports the revenue in its own events. If they come from different tags, or one includes tax and shipping and the other does not, they differ even on the same sales.

Which number to use

Use Google Ads to manage Google Ads, and GA4 to decide what your marketing earned. Do not add the two together, and do not expect them to match.

• Bidding and optimising inside Google Ads: its own conversions. They are what its bidding learns from, and they line up with its clicks.
• Comparing channels, or spend against revenue: GA4. It is the one place that sees every channel and counts each sale once, so its numbers add up across your marketing as a whole.
• Checking that tracking works: compare the two over a long period, like a full month, with the most recent week left out. A steady gap is the differences above. A sudden change in the gap usually means a tag broke.

How Glancely handles it

On Glancely's Revenue page, spend comes from Google Ads and revenue from GA4, on one row per channel and per campaign. We show one revenue number, not two: putting Google Ads' conversion value beside GA4's would raise exactly the question this article answers, on every row. Campaigns are matched by name, and where a campaign cannot be matched, the page says so rather than showing it as having earned nothing.