A method, computer program product, and system for determining a number of users corresponding to a server load including simulating one or more virtual users on a test computer system on coupled to network. One or more client requests are sent from each of the one or more virtual users to a server application executed on a server computer system coupled to the network. A metric indicative of a load on the server computer system is measured. The metric is compared to a predetermined value; and the number of the one or more virtual users is changed based on the difference between the metric and the predetermined value until the metric is within a predetermined range of the predetermined value.