Capacity Utilization
ρ (rho)The percentage of available capacity that is actually being used.
Also known as: Utilization Rate, Resource Utilization, Loading
Capacity utilization measures how much of a process step’s capacity is consumed by actual work. A step running at 50% utilization is idle half the time. A step at 100% is working at its maximum, and any increase in demand will create a backlog.
In people-driven processes, utilization can temporarily exceed 100% if employees speed up or overtime is accumulated, but this isn’t sustainable long-term.
Formula
ρ = Throughput / Capacity (expressed as a percentage)
Example
A work centre has a capacity of 20 units per hour. Current throughput is 10 units per hour. Capacity utilization = 10 / 20 = 50%.
The work centre is idle 50% of the time. If you reduce staff (lower capacity to 12), utilization rises to 83%, more efficient use of resources, but less buffer for demand spikes.
Why It Matters
Utilization directly affects cost per unit, higher utilization means costs are spread over more output. But pushing utilization too high leaves no buffer for variability, and wait times increase exponentially as utilization approaches 100%. The optimal utilization depends on how variable your demand and process times are. Highly variable processes need more buffer (lower target utilization); stable processes can run closer to capacity.