This paper discusses a method for directly converting a set of binary interaction parameters of a thermodynamic model to that of another thermodynamic model without calculating phase equilibria. The proposed method assumes that the excess Gibbs energy calculated by the original model at a liquid condition is equivalent to that by the other model. To remove iterative procedures in these calculations, an empirical correlation for liquid molar volume is proposed to analytically derive activity coefficients from the equation of state. Performance of the method is examined in obtaining binary interaction parameters of an empirical mixing rule for the SRK equation of state from those of NRTL or molecular sub-group contribution parameters of UNIFAC. (C) 2010 Elsevier B.V. All rights reserved.