Workload capacity: ability of our cognitive processing mechanisms to respond to the changes in task demands that influence the workload. These include changes to the number of subtasks within a task, items in a visual or memory search display, and manipulated features in a visual processing task. Blaha will discuss a human information processing modeling perspective on workload capacity, from which we measure mental work with hazard functions of response time data. Capacity Coefficient measures of workload capacity will be defined based on comparison of observed performance to baseline unlimited capacity models. These model-based measures are non-parametrically defined on empirical response time data, and the non-parametric nature makes them flexible and broadly applicable across perception and decision making tasks. The use of the capacity coefficient on motor movement time in human-computer interaction and cognitive response time visual decision making tasks will be illustrated, and efforts moving these models into dynamic, multitasking environments will be discussed.