In this work, an analytical model for the subthreshold swing of double gate and cylindrical nanowire MOSFETs is proposed. Using the Voltage Doping Transform, it is shown that a one-dimensional potential model is sufficient to obtain a high accuracy, provided that an effective oxide thickness is used. The validity of this model is then confirmed with TCAD simulations. Finally, the impact of quantum effects is discussed. Based on Density-Gradient simulations of Si and GaAs MOSFETs, it is shown that the model is still valid when quantum effects are accounted for. (C) 2015 Elsevier Ltd. All rights reserved.