This paper describes a set of methods and related tools developed for incorporating cost into force-structure decisions involving a mix of Active Component (AC) and Reserve Component (RC) units of particular types. The development effort was initiated in response to Objective 1 of the “Comprehensive Review of the Future Role of the Reserve Component,”1 which sought the development of a consistent, widely accepted cost methodology for determining force mix. Determining the best mix of Active and Reserve units is an important element of defense planning and force sizing. Active units are often better able to deploy on short notice than Reserve units, and can be deployed more frequently. Reserve units, on the other hand, are less expensive on a unit-for-unit basis, allowing a larger force structure to be maintained for a given level of expenditure. We have developed this methodology and set of associated computer-based tools to facilitate comparison of alternative AC-RC force mixes for the Office of the Secretary of Defense (OSD), the Joint Staff, and the Services.