A technique that institutional researchers can use to assist department chairpersons in balancing student needs and faculty resources is described. Basic institutional research office data is combined with departmental data so that the department heads can justify their needs, plan recruiting, select students to achieve a balance of faculty resources, and accommodate the instructional needs of student majors and student nonmajors. The approach is illustrated using the example of a psychology department. A second illustration examines two departments that used critical mass data to evaluate the effects of a merger. The results indicate that cost data generated for funding purposes and student curriculum patterns can be converted into data that are directly useful to academic department chairpersons. The proposed solutions affect the balances between ideal and actual ratios, the major to nonmajor mix, and the FTE faculty and student counts. It is suggested that direct applications of critical mass evaluation provide the institutional research office with the opportunity to increase their service to academic departments. It is also suggested that critical mass evaluation enables department chairpersons to make realistic academic decisions based on budgetary constraints. (Author/SF)