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The most common question about load testing is “how many virtual users do I need to simulate”. The simplest answer is “how many users or page views do you want to accommodate on your website or web application without crashing?

Determining the exact number of virtual users for a load test is always a tricky question, for novice and seasoned load testers alike. There are numerous ways of finding the required number of virtual users while evaluating a Load testing tool, selecting a pricing plan or running a load test. The calculations on this page will help determine the number of virtual users required to run a load test.

Note: This calculator gives a reference or guesstimate of the number of concurrent users required for running a load test. This calculator should not be used to estimate the number of pages that will load within aspecific time interval.  

Peak Hour Page Views
[Expected]
 
Session Length in Seconds
[ =Page Load Time + User Think Time]
 
Concurrent Users

Peak hour page views:

The goal of load testing is to determine the volume of page views or transactions your site can accommodate without breaking. You can get peak hour page views from your web analytics team or tools such as Google analytics. Generally, the target number of page views should be based on the application’s future peak hour of usage. Let’s say you run an ecommerce site, and last holiday season your site experienced 10,000 page views during peak hour and you expect the traffic to increase by 25% this year. In this case start with the peak hour page views of 12,500 to better prepare for the upcoming traffic surge.

Another way to determine page views is by reverse engineering checkouts or conversions. Ex. Your site can handle 1000 checkouts in an hour and you have a 10 step checkout process. So the total number of page views for this process is 10 steps x 1000 transactions = 10,000 page views.

Session Length

Per Google Analytics support page: A session is a group of interactions that take place on your website within a given time frame. For example a single session can contain multiple screen or page views, events, social interactions, and ecommerce transactions. Session length comprises on page load time and user think time.

Concurrent Users

A concurrent user runs through a transaction from start to finish, and then repeats until the test is over. A “unique user,” on the other hand, is simply a single execution of a concurrent user or the completion of one transaction (execution of the test script from start to finish). Depending on a number of factors, concurrent users are able to generate the traffic.