makespan
The time difference between the start and finish of a sequence of jobs or tasks.
Makespan: total elapsed time from job start to finish
Makespan is the wall-clock duration from when the first job enters a production line or system until the last job exits. It measures the total time span required to complete an entire batch or schedule of work. In a job shop, for example, if the first part starts machining at 08:00 and the final part leaves inspection at 16:30, the makespan is 8.5 hours, regardless of how much idle time individual machines experience.
The term matters because it is not the same as the sum of individual job times. Three jobs taking 2 hours each do not have a 6-hour makespan if they run in parallel on different machines. Makespan depends entirely on the order of jobs, machine availability, bottlenecks, and idle time between operations. Reducing makespan means completing the entire schedule faster, which increases throughput and frees equipment for the next batch sooner.
Scheduling and bottlenecks
In manufacturing, makespan is central to scheduling problems. The goal is usually to minimize it, which requires balancing load across machines and arranging job sequences to avoid starving downstream operations. A single slow machine or a poorly ordered sequence can extend makespan dramatically even if most of the shop floor sits idle. This is why dispatching rules, like shortest processing time or critical ratio, aim to keep work flowing and compress the total elapsed time.
Makespan differs from cycle time, which is how often a job completes under steady production. A factory might have a cycle time of 15 minutes per unit but a makespan of 40 hours for a 100-unit order, because cycle time assumes pipelined, continuous operation whereas makespan accounts for setup, changeovers, and the actual beginning and end of the run.
The name reflects its literal meaning: the span of time the job makes as it travels through the system. It is a practical metric used in production planning, contract estimating, and capacity planning. Understanding your makespan helps predict when finished goods will ship and whether a new order can fit before a deadline.