It's one of the most common questions we hear: "Google Ads says one number for last month's conversions, and Google Analytics says another. Which one is right?"
Often, both are. GA4 and Google Ads measure different things, for different purposes, using different rules. Google itself says discrepancies between the two are common and can occur even with a correct setup.
That doesn't mean every gap is harmless. Here's how to tell the difference.
Clicks and sessions are different things
Google Ads counts clicks on your ads. GA4 counts sessions, which are visits to your website. Google's troubleshooting guide says some discrepancy is expected. For example:
- If someone clicks your ad twice within 30 minutes without closing their browser, Google Ads records two clicks, but GA4 may count one session.
- If someone clicks your ad and leaves before your page (and its tracking code) has loaded, Google Ads records a click but GA4 never sees a session.
- Google Ads filters out clicks it considers invalid. GA4 doesn't apply the same filtering.
- GA4 can show more sessions than clicks, because a returning visitor's later sessions can still be credited to the original campaign. Google describes this as a sign of positive engagement.
Conversions are dated differently
This is the difference we see catch people out most often. Google Ads reports a conversion against the date of the ad click that led to it. GA4 reports it on the date the conversion actually happened.
Google gives a simple example: someone clicks your ad on 19 July and buys the next day. Google Ads records the sale on 19 July; Analytics records it on 20 July. Across a month-end, that alone changes the totals.
To compare fairly, Google suggests adding the "Conversions (by conv. time)" or "All conv. (by conv. time)" columns in Google Ads when comparing with Analytics, as these use the conversion date instead.
Each tool counts and credits conversions its own way
Attribution. An attribution model decides which channels get credit for a sale. GA4 lets you choose a reporting attribution model and which channels can receive credit. By default, GA4 reports give credit across paid and organic channels, while Google Ads reports default to Google paid channels. So the same sale can be credited differently in each tool.
Windows. Google Ads only records a conversion if it happens within the conversion window you've set, anywhere from 1 to 90 days depending on the source. GA4 has its own key event lookback window. If they're set differently, one tool will include conversions the other leaves out.
Counting. Google Ads can count "Every" conversion after a click or just "One". If someone fills in two lead forms after one ad click, GA4 shows two key events, while Google Ads set to "One" reports one.
Columns. The main "Conversions" column in Google Ads only includes actions set as "Primary". The "All conversions" column also includes secondary actions and, depending on your setup, view-through conversions.
Key events, conversions and two different tags
GA4 now calls important actions key events, and reserves conversions for actions shared with Google Ads. Google explains the difference and notes they can use different attribution settings.
Many businesses also track the same action twice: once as an imported GA4 key event and once with a Google Ads conversion tag. These won't always agree, partly because Google Ads conversion tracking only measures conversions from Google Ads. It's worth knowing which one your campaigns bid on.
Modelled data, consent and cross-device journeys
Not every conversion can be observed. Visitors switch devices, browsers limit cookies, and some people decline cookies. To fill these gaps, Google uses modelled conversions, estimated from patterns in the data it can observe. Google Ads also models cross-device conversions.
Consent Mode plays a part here. In advanced mode, when visitors decline cookies, Google's tags send limited "cookieless pings" that Google uses for modelling; basic mode relies on a more general model. We explain more in our guide to Consent Mode v2 for small businesses.
A quick word on the law. In the UK, cookie consent is governed by the UK GDPR and the Privacy and Electronic Communications Regulations (PECR). Google's EU user consent policy covers the UK, but Google says it doesn't currently expect advertisers to send a verified consent signal for UK or Swiss traffic, only for traffic from the EEA. Moving tracking to a server doesn't remove the need for consent either (here's why). This is general information, not legal advice, so please check with a data protection specialist if you're unsure what applies to you.
Smaller things that add up
- Time zones. GA4 reports in your property's time zone and Google Ads in your account's. If they differ, conversions near midnight can land on different days.
- Processing delays. Google suggests allowing 24 to 48 hours for data to sync, and says GA4's attributed conversion data can update for up to 12 days.
- Data thresholds. GA4 may withhold some data, such as demographics, to protect privacy. A wider date range can help.
- Lost click IDs. Auto-tagging adds a click identifier (the GCLID) to your ad links. Redirects that strip it out can leave paid visits showing as organic, direct or "(not set)".
Your GA4 vs Google Ads sanity checklist
Before deciding there's a problem, work through these:
- Confirm the accounts are linked, and only compare dates after linking, as data isn't filled in retrospectively.
- Check auto-tagging is on in Google Ads.
- Match the time zones of your GA4 property and Google Ads account, or allow for the difference.
- Compare by conversion time using the "(by conv. time)" columns in Google Ads.
- Compare like with like: Ads clicks with GA4 sessions from Google Ads, and the same conversion action in both.
- Check your columns: "Conversions" (Primary only) or "All conv.".
- Review your settings: attribution model, channels that can receive credit, conversion window, lookback window and counting method. Don't assume the defaults.
- Look for duplicate tracking: a GA4 import and an Ads tag measuring the same action, both Primary.
- Test your landing pages: add
?gclid=testto a URL and check it survives any redirects. - Leave recent data to settle before drawing conclusions.
- Look for a sudden change. In our experience, a steady gap is usually normal; a gap that jumps after a site or tag change usually isn't.
If you've recently changed your tag setup, our round-up of the 2026 GTM updates may also help.
Trusting your numbers again
GA4 and Google Ads will never match exactly. The goal is to understand why they differ, so you can trust each for what it's good at: Google Ads for judging campaigns, GA4 for understanding your whole website.
If you'd like a second pair of eyes on your tracking, or help working out whether a gap is normal, take a look at our services and get in touch.
Sources: Google Ads Help, "Create conversions from Google Analytics events in Google Ads"; Google Ads Help, "Clicks and Sessions Discrepancy for Google Ads and Google Analytics: Troubleshoot"; Google Ads Help, "Data discrepancies: Factors and troubleshooting"; Google Ads Help, "About conversion windows"; Google Ads Help, "About consent mode"; Analytics Help, "Select attribution settings"; Analytics Help, "Conversions vs. key events in Google Analytics"; Analytics Help, "[GA4] About modeled key events"; Analytics Help, "[GA4] About data thresholds"; Google, "Help with the EU user consent policy".