Process Capacity
µThe maximum number of units a process can produce per time period when running at full utilization.
Also known as: Maximum Capacity, Nameplate Capacity, Design Capacity
Process capacity answers “how much can this process do?” For a single work center, capacity equals the process rate. For a serial process with multiple steps, the capacity equals the capacity of the slowest step (the bottleneck). The process cannot produce more than its weakest link allows.
A high capacity is preferable: it processes work faster, at lower cost per unit, recovers from errors more quickly, and is more flexible to changes in demand.
Formula
Single step: µ = r (capacity equals process rate)
Serial process: µ = MIN(µ₁, µ₂, ..., µₙ) (capacity of the bottleneck)
Example
A process has three steps with capacities of 20, 15, and 25 units per hour. The process capacity is 15, the minimum of the three. Even though steps 1 and 3 can handle more, the process can only output what step 2 can handle.
If you add a second worker to step 2, its capacity doubles to 30. The process capacity now becomes 20 (step 1 is the new bottleneck).
Why It Matters
Capacity is the ceiling on your process output. Too little capacity means work backs up and wait times increase. Too much capacity means you’re paying for resources that sit idle. The goal is to match capacity to demand, or slightly above it, at the bottleneck. Capacity decisions at non-bottleneck steps have limited impact on overall process performance.