A parametric equation for describing polarization in solid oxide fuel cells (SOFC) is presented in terms of experimentally measurable parameters. The equation explicitly describes activation and concentration polarizations at the two electrodes, and the ohmic loss as a function of current density. Using the equation and known values of experimentally measured parameters, determined by in-cell and out-of-cell tests, various polarizations are estimated as functions of current density, and the maximum possible performance characteristics are assessed. The parameters used for the calculations of polarization curves include: (a) Charge transfer resistivity as a function of temperature and atmosphere measured using patterned electrodes deposited by micro photolithography. (b) Effective gas phase diffusivities measured using an electrochemical technique or from prior cell performance fitting. (c) Estimated ohmic loss using in-cell and out-of-cell measurements. Polarization curves are calculated for two different microstructures in the functional layers. Calculations are also made for various compositions of the fuel, which can be used to estimate performance as a function of fuel utilization, and various oxidant compositions. Then, using the model, prospects for ultra-high power density SOFC at intermediate temperatures (<800oC) are examined. The results show that even in thin electrolyte film, anode-supported cells, ohmic contribution can be substantial. The results also show that the electrode particle size has a substantial effect on activation polarization.