Capacity Utilization Rate

What Does Capacity Utilization Rate Mean?
A metric used to measure the rate at which potential output levels are being met or used. Displayed as a percentage, capacity utilization levels give insight into the overall slack that is in the economy or a firm at a given point in time. If a company is running at a 70% capacity utilization rate, it has room to increase production up to a 100% utilization rate without incurring the expensive costs of building a new plant or facility.

Also known as "operating rate".

Graphically:

Investopedia explains Capacity Utilization Rate
Capacity utilization rates can also be used to determine the level at which unit costs will rise. For instance, let's say that Company XYZ currently produces 10,000 widgets at a cost of $0.50 per unit. If it is determined that it can produce up to 15,000 widgets without costs rising above $0.50 per unit, the company is said to be running at a capacity utilization rate of 66% (10,000/15,000).

This is best applied to companies that produce physical goods rather than services, as the capacity measurements are much easier to quantify.