Although the nature of their gaits is similar, planar bipeds with curved feet have been shown experimentally to be more energetically efficient than those with point feet. Further, both healthy human feet and prosthetic feet can be modeled as a circular arc with the center of curvature in front of the shank. Thus, understanding the effects of a curved foot's properties on the energetic cost of gait and on gait kinematics has the potential to improve both bipedal robots and prosthesis design. To date, there has not been a systematic study of the effects of changing the foot radius and center of curvature location on symmetric bipeds. This paper explores the effects of changing the curved foot's geometric properties for both two- And five-link planar, under actuated bipeds with instantaneous transfer of support at impact. It is found that the foot radius has a substantial effect on the energetic efficiency of a gait regardless of the morphology of the biped. The effect of foot center of curvature location on energy efficiency is dependent on the morphology of the biped and is much less significant than the effect of foot radius. Both the foot radius and center of curvature location affect the knee kinematics of the five-link biped. The foot radius affects the hip kinematics of the two-link biped.