Throughout literature, there are two approaches to estimate fuel cells (FC) performance, by the evaluation of polarization curve. One includes, physical modelling of heat and mass transfer with electrochemical phenomena; the second is based on semiempirical equation used in order to analysis the effect of different physical perturbation on the polarization curve and consider FC as a black box. The aim of this study is to present a simple but enhanced and accurate expression of PEMFC output voltage. The model includes operative conditions, current density and geometric parameter of the FC.