This report documents the MINIFAST model of the Navy's enlisted personnel system. The assumptions made and formulas used in computations are presented in detail, along with a general view of the modelling approach. The model, beginning with the selection of a subject rating, calculates an estimate of the yearly gains and losses of personnel, the promotions within, and the new recruits to the rating. A policy affecting the personnel system can be quickly evaluated for its effect on overages and shortages of personnel, its effect on the advancement system, and the need for new personnel, for multiple years in the future. Thus MINIFAST is an interactive planning model for rapid policy evaluation.