Knowledge of metastable zone width (MZW) can help to control the quality of the produced crystals. In this study, the maximum MZW in adductive crystallization of Bisphenol-A (BPA) from a phenolic solution was determined using the concepts of thermodynamic phase equilibria. Using these concepts, it was possible to determine the maximum MZW in the absence of the influence of the kinetic factors such as the rate of cooling, and the rotational speed of the mixer. The method included calculating the necessary parameters in various excess Gibbs energy models, and determining their temperature dependencies. The excess Gibbs energy models studied were the Symmetrical, Margules, Wilson, and NRTL models. Experimental transparency (solubility) and cloud point (instability) data were obtained for five different binary solutions of phenol containing 9.5, 13, 18, 23, and 25 wt% BPA. Calculations showed that the Margules and Symmetrical models were able to predict the maximum MZW.