flowtime

Flowtime is a term used in manufacturing, production planning, and operations research to denote the total time a unit spends in a system from its entry to its completion. In scheduling theory, a unit’s flowtime is defined as the difference between its completion time and its release (or arrival) time, i.e., F = C - r. This encompasses all time the unit spends: waiting in queues, being processed, and any setup or transfer times within the system.

Flowtime is related to, but distinct from, other timing measures. Lead time generally refers to the time from customer order to delivery, including external processes; cycle time refers to the time to complete a unit at a given station or step. Flowtime is often used as a performance metric to assess responsiveness and efficiency and as an objective in scheduling models, for example by minimizing the sum of flowtimes across a set of jobs.

Measurement requires tracking timestamps for each unit’s arrival, processing start, processing end, and departure. In practice, reductions in flowtime reflect reductions in waiting and smoother production flow. However, focusing solely on flowtime can cause trade-offs, such as increased work-in-process or the prioritization of short jobs at the expense of longer ones.

In service settings and software development, similar concepts are used under names like sojourn time or throughput time, indicating the time from a request’s arrival to its fulfillment.