Configuring a load test requires you to set up a test load that reflects real-world behavior.  In other words, to receive the most relevant test results, you need to specify the realistic number of concurrent users to simulate during the test at the target web resource.

Concurrent users represent how many users will visit your website and perform specific transactions at exact same time interval (but not the same step of the transaction all at once).

Web analytics tools can be a great resource in order to determine relevant traffic data, such as user visits statistics and duration of sessions on a website. However, it’s often hard to tell the exact number of concurrent users on the site right away. You can see hundreds of visits per hour in the analytic report, but the site actually may have only two concurrent visitors at the time.

 

In this article, we will show how to use a Google Analytics reports to determine the number of concurrent visitors for a web site.

Using Web Analytics to Calculate Concurrent Users

Google Analytics, as well as some other web analytics tools, can provide you with the Sessions metric your website has per a regular time interval and the Average Session Duration for the selected interval. To translate these metrics into concurrent users, you need to find Hourly statistics (Google Analytics > Reporting > Audience > Overview > Hourly) and get Sessions and Avg. Session Duration for the same time frame.

For LoadView calculations, all times are defined in minutes.

Use the following formula to estimate the number of concurrent users:

Concurrent users = Hourly Sessions x Avg. Session Duration (in minutes)/60 

For the analytics provided in the picture above, the number of concurrent users equals:

Concurrent users = 7,727 x 9/360 = 19

While the average traffic statistics can work well to set up a realistic test, it is more significant to use statistics of peak traffic periods to configure a test.

For example, during peak hours of traffic, your site analytics shows the peak number of sessions per hour equal to 1,000 sessions. Let’s say the Avg. Session Duration value for the interval is five minutes.

In this case, the number of concurrent users that should be simulated to create 1,000 visits per hour is:

Concurrent users = 1,000 x 5/60 = 83

Using Custom Parameters

If you don’t have web analytics data, you can use the expected number of user visits to calculate the number for concurrent users:

Concurrent users = Number of expected visits per minute * Visit Duration (in minutes)

Example:

Let’s say we expect 100,000 users to visit our website per day. This is equal to 100,000/24 = 4,166.66 per hour. For this example, we’ll approximate to 4,200 per hour.  Next, to find the number of visits per minute, we take 4,200/60 = 70 visits per minute. If the predicted visit duration is 30 seconds (or 0.5 minutes), the number of concurrent users that should be simulated to create 70 visits per minute is:

Concurrent users = 70*0.5 = 35

This means a single virtual user can run two sessions per minute (1 minute/0.5 minute = 2 sessions per minute). In this case, we need LoadView to simulate 35 virtual users to emulate 70 visits on the target website for a minute.