A porous metal was suggested to be used for the anode of a DCFC. Thermo-fluidic characteristics of fuel-electrolyte mixture in the porous metal should be known in order for proper design of the anode. Previous researchers investigated pressure drop and heat transfer performance of fluids flowing through metal foams that have different pore densities and porosities. Various characteristic length scales were used for the Reynolds number and friction factor of metal foams in the previous works. In the present study, we propose a realistic definition of the characteristic length scale that is applicable to pressure drop evaluation in metal foams regardless of pore density and porosity. A series of experiments was conducted to obtain friction factor of metal foam. An equivalent diameter based on permeability and porosity appeared to best fit the experimental data produced using various metal foams. The relationship between the friction factor and Reynolds number through metal foams can be classified into three regimes. In Re < 20, ln f is inversely proportion to ln 16/Re. In Re > 2000, the value of friction factor approaches 0.17. The relationship between friction factor and Reynolds number of foam materials appeared to be similar trend to that of Moody chart. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.