This study investigates two methods to determine the contact area between a N95 filtering facepiece (NFF) respirator and a headform. Five size headforms (large, medium, small, long/narrow and short/wide) wear a NFF respirator (3M 8210) respectively. A biofidelity finite element model of headform is built to simulate its interaction with a NFF respirator. During the simulation, the respirator contacts the headform. Two methods are presented in this paper for determining contact areas: The first one is through the observation of contact pressure distribution. The assumption is that the contact area is the fraction of surface area with positive contact pressure. The second method is through extracting the intersecting area between deformed surfaces of the headform and NFF respirator. Finally, the experiment, which directly measures the dimensions of contact area between prototypes of the headform and the NFF respirator, validates the proposed methods.