InformWhen evaluating the success of marketing campaigns, conversion rate remains one of the most crucial metrics, helping marketers compare campaign performance across varying traffic levels. However, in Google Analytics 4 (GA4), finding this essential metric wasn’t straightforward - initially absent from the default acquisition reports in the “Reports” workspace.
Responding to widespread feedback, Google has now made conversion rate (renamed key event rate in GA4) a standard feature in both the “Traffic Acquisition” and “User Acquisition” reports as of June, 2024. This change aligns with the platform's updated terminology, where conversions are now referred to as key events.
Here we’ll look at how to find and interpret this metric in GA4 reports.
How to use the ‘session key event rate’ in the traffic acquisition Report
The “Traffic Acquisition” report evaluates session performance based on traffic sources such as channel, source, medium, or campaign. Within this report, you can scroll to the right to locate the “session key event rate” metric, which Google defines as “the percentage of sessions in which any key event was triggered.” The metric is calculated using the following formula:
Session key event rate = (Number of sessions with a key event) / (Total number of sessions)
It’s essential to note that multiple key events can be recorded during a single session, so the “session key event rate” will not simply equal the total number of key events divided by the total number of sessions.
Let’s explore this concept further with an example scenario for Paid Search sessions:
We have 5 sessions, 2 included key events, giving us a session key event rate of 40% (2/5 * 100 = 40%).
One of the key benefits of using the Reports workspace and the Traffic Acquisition report is the ability to filter the key event rate by specific key events. This allows you to see the percentage of sessions where a particular event was triggered, relative to the total number of sessions.
For example, if we filter the previous scenario to focus on a specific key event like “generate_lead,” the number of key events considered will decrease, as illustrated below:
In this case, only 1 out of 5 sessions triggered the "generate_lead" key event, resulting in a session key event rate of 20% (1 session / 5 sessions * 100 = 20%).
Remember, you can easily access this metric in the “Traffic Acquisition” report within the Reports workspace, as shown below:
How to use the ‘user key event rate’ in the user acquisition report
The key event rate is also available in the User Acquisition report, but here it’s calculated at the user level rather than by sessions. In this case, it measures how many users triggered at least one key event out of the total number of users. This approach helps mitigate instances where a single user converts multiple times across different sessions, as each user is only counted once.
To illustrate this, let’s consider an example: if we acquire 3 unique users from Paid Social, each with different journeys, as shown below:
Even though user 1 had multiple sessions where a key event was recorded, they are still counted as one unique user who converted, just like user 2. As a result, the user key event rate for the Paid Social channel in this example would be 66.67% (2 users / 3 users * 100 = 66.67%).
Below is a screenshot showing where you can find the user key event rate metric in the User Acquisition report:
How to use the ‘key event rate’ metric in Explore
The user key event rate and session key event rate metrics can also be included in free-form reports within the Explore workspace. However, there are a few important considerations when using these metrics in Explore.
First, since you need to select your dimensions and metrics to build the report, it’s easy to accidentally combine them incorrectly—especially with the key event rate metric. To accurately analyze the user key event rate, ensure you pair it with user-scoped traffic source dimensions.
Similarly, when analyzing the session key event rate, you must combine it with session-scoped traffic source dimensions.
Also, in the Explore workspace, the key event rate metrics cannot be filtered by a specific key event; they are calculated based on all key events collectively.
Below is an example of a free-form report showcasing the session key event rate for reference:
In summary, both the user key event rate and session key event rate metrics provide valuable insights for understanding user behaviour and campaign performance in GA4. By using the User Acquisition report, you can focus on how individual users are converting, while the Traffic Acquisition report gives you session-level analysis. When working in the Explore workspace, ensure you pair these metrics with the correct dimensions for accurate reporting, and remember that filtering by specific key events is not currently possible.
To deepen your understanding of GA4 reporting and improve your campaign analysis, consider registering for our Introduction to Google Analytics 4 Reporting course. If you want to take things further you can also check out our Advanced Analysis course.
Matthias Morin
