To better understand a process, Process Lead Time may be calculated. This calculation is an foundational metric for both Lean and Six Sigma, or what is commonly referred to now as Lean Six Sigma.
The formula for Process Lead Time = Work in Process (WIP) / Average Completion Rate.
Work in Process is anything that has entered the system and has not yet come out. More than just the physical materials found in manufacturing, Work in Process can be unanswered emails, customer requests, etc. For example, a team is currently working on five reports and the Average Completion Rate is 2 hours. The Process Lead Time is calculated as 5 / 2 = 2.5. To decrease the Process Lead Time, either the WIP may be decreased or the Average Completion Rate can be increased. Process Lead Time is also used to calculate Process Cycle Efficiency (PCE).