The mathematical model of the Molten Carbonate Fuel Cell (MCFC) is presented. The new approach for modeling the voltage of MCFC is proposed. Electrochemical, thermal, electrical and flow parameters are collected in the 0-D mathematical model. The aim was to combine all cell working conditions in as a low number of factors as possible and to have the factors relatively easy to determine. A validation process for various experimental data was made and adequate results are shown. The presented model was validated for various fuel mixtures in relatively wide ranges of parameters. A distinction is made between the "design-point" and "off-design operation". Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.