The purpose of this thesis is to model the output factors that affect the number of monitor units (MUs) required to deliver a prescribed dose with a passively scattered proton beam in Gantry 1 at Loma Linda University Medical Center (LLUMC). Parameters that can affect the MUs include the beam energy, the effective field size, bolus thickness, air gap, and the calibration point depth. Field Size Factors (FSFs), Bolus-Gap Factors (BGFs), and Depth Dose Factors (DDFs) were experimentally determined. Using normalization techniques and linear interpolation between data points, a MU Model was created. This MU Model was compared with output factors and MUs determined during patient specific calibrations. Less than 1% error exists between the MU Model and the patient specific calibration output factors and MUs. My MU Model is currently being compiled into a user friendly format that can be implemented clinically in Gantry 1 at LLUMC.