Little’s Law states that the size of a queue (the number of items in WIP status) is proportional to the duration of time in the queue. Therefore, the goal of Lean and Agile is to reduce cycle times to a minimum.
WIP limits prevent them team from taking on too much work and reveal the bottlenecks. Teams get their work done faster by limiting the amount of Work-in-Progress.
The relationship between WIP and cycle time is expressed by the following equation
Work-in-progress (WIP) = Lead Time * Throughput
The Lead time for a process is equal to the number of jobs to be executed divided by the average time to execute each job