JCalculus is a Workload Modelling or Workload Distribution tool. JCalculus can help you determine the maximum number of VUsers that can be run on a Load Generator based on VUser memory footprint. JCalculus can also help you derive ThinkTime and Pacing using Little's Law for performance testing. Little's law is applied to relate concurrent users, server's throughput & total time consumed.

Transactions per Hour
Transactions per Second
Avg. Response Time (Secs)
Think Time + Pacing (Secs)