In this article, the effects of process variations on the circuit model parameters of planar rectangular spiral inductor implemented using Gallium Arsenide (GaAs) technology are presented. The effects of variation in line width on the inductor circuit model parameters are investigated using electromagnetic simulation. Simple formulas to account for these effects using curve fitting are proposed. This is advantageous to the circuit designer in that the nominal inductor models can be easily modified to account for these variations and can be helpful during circuit design optimization. © 2010 Wiley Periodicals, Inc.