What is Makespan? Definition & Manufacturing Examples

What is Makespan?

Makespan is the total elapsed time from the beginning of the first job to the completion of the last job in a set of production work. It measures how long it takes to process an entire batch of orders through the shop, from the moment production starts until every job is finished. Makespan is one of the most commonly used objective functions in scheduling optimization — minimizing makespan means getting all work done in the shortest possible time.

How Makespan Works in Manufacturing

Makespan depends on how jobs are sequenced across resources and whether operations can run in parallel. For a single machine processing 5 jobs sequentially, makespan is simply the sum of all setup and run times regardless of sequence. But in a multi-machine environment where jobs have multiple operations on different resources, the sequence matters enormously.

Consider a shop with two machines where Job A needs Machine 1 then Machine 2, and Job B needs Machine 2 then Machine 1. If Job A starts first on Machine 1, Machine 2 sits idle until Job A's first operation completes. The choice of which job starts where directly affects how much idle time occurs and therefore the total makespan.

Minimizing makespan is particularly valuable when you have a fixed set of work to complete — such as a weekly production plan or a project with multiple work orders. By finding the sequence and resource assignments that minimize total elapsed time, you effectively increase the throughput of your facility without adding resources.

The tradeoff is that minimizing makespan does not always minimize individual job lateness. A schedule that minimizes total makespan might make some individual jobs later than a schedule optimized for on-time delivery. Planners must choose the right optimization objective for their situation.

Makespan Example

A shop has 3 machines and 4 jobs to complete. The total processing time across all jobs is 48 hours. With naive scheduling — assigning jobs to machines without optimization — the makespan is 22 hours because of idle time between operations.

After the scheduling system optimizes the sequence:

• Machine 1 runs continuously from hour 0 to hour 16 with no gaps
• Machine 2 runs from hour 1 to hour 17 with only 1 hour of idle time
• Machine 3 runs from hour 2 to hour 18 with 2 hours of idle time

Optimized makespan: 18 hours — a reduction of 4 hours (18 percent) from the unoptimized schedule. Those 4 hours represent recovered capacity that can be used for additional work or earlier completion of the entire batch.

Why Makespan Matters for Production Scheduling

Makespan optimization is valuable for manufacturers who batch-process work on a weekly or daily cycle. By minimizing the total time to complete each batch, the shop increases effective capacity, reduces per-unit overhead costs, and creates buffer time for unexpected rush orders or disruptions.

Scheduling tools like Resource Manager DB (RMDB) optimize schedules to minimize makespan while respecting due date constraints. The system evaluates thousands of possible sequences to find the arrangement that completes all work in the shortest time, then displays the result on an interactive Gantt chart where planners can review and adjust the schedule.

Related Terms

• Throughput — The rate of production output, which increases as makespan decreases for a fixed set of jobs
• Critical Path — The longest sequence of dependent operations that determines the minimum possible makespan
• Job Sequencing — The process of ordering jobs to optimize objectives like makespan

Frequently Asked Questions

Learn more in our complete manufacturing glossary or production scheduling guide.