We propose here a simple approximate, yet accurate, formula to easily calculate the maximum magnitude of the electric potential at the channel width's midpoint of symmetric Double Gate (DG) MOSFETs with any arbitrary body doping concentration. According to it this maximum magnitude depends only on the body's thickness and doping concentration, apart from its usual dependence on quasi-Fermi level splitting. The new formula allows to easily determine the critical body thickness value above which any arbitrarily doped symmetric DG MOSFET can be satisfactorily modeled using a conventional bulk MOSFET model. This critical value depends only on body doping concentration. The proposed approximate formula also constitutes a useful means to quickly calculate initial values in iterative numerical calculations of doped symmetric DG MOSFET models. (C) 2012 Elsevier Ltd. All rights reserved.