In this paper, an optimal selection methodology for the number of phases will be proposed for an interleaved boost converter (IBC). Also, the analysis of the input current ripple according to CCM and DCM is carried out. The proposed design methodology will be theoretically analyzed, and its validity verified by simulation as well as with experimental results. Moreover, a comparison of cost and efficiency based on a 600W laboratory prototype using the Ballard NEXA 1.2kW PEMFC system is demonstrated.