This paper presents a detailed model to evaluate power density, species concentration, operating current/voltage, efficiency and temperature of a solid oxide fuel cell (SOFC) operating under direct internal reforming conditions. The computational framework, at the unit-cell level, encompasses a detailed 42-step reaction pathway for heterogeneous chemistry in the anode structure (Ni based catalysts), modified Butler-Volmer formalism to represent charge transfer chemistry, Dusty Gas Model for the porous media transport and a simple 1D solid-phase heat balance model. Simulations are performed for configurations ranging from simple 1D electrochemical cells to quasi-2D unit cells to complex 3D stacks, to elucidate the effectiveness of the tool for performance and design optimization. © The Electrochemical Society.