A procedure is proposed to convert back and forth between two equations used to model the saturation current of thin film transistors. To demonstrate and determine the effectiveness of the proposed procedure, experimental data modeled by the traditional monomial (power-law) model is transformed into a recently proposed polynomial model. Conversely, another set of data, which was originally represented by the polynomial model, is transformed to the monomial model. This procedure is also applied to short-channel crystalline MOSFETs.