Abstract A new parameter, pseudo temperature ( T p) is introduced to solve two-phase equilibrium calculations. The resulting T p-method has a single set of equations to describe different phase regions encountered in vapor-liquid equilibrium (VLE) and liquid-liquid equilibrium (LLE). It does not require a priori the number of phases existing at equilibrium, and involves a minimization problem having a linear objective function subject to nonlinear constraints, which can be solved by a version of successive linear programming method. T p-method is tested on typical examples for VLE and LLE, and compared with pseudo pressure ( P p) method of Bullard and Biegler [ Computers and Chemical Engineering 17, 95–109 (1993)] for VLE. In each example, several operating conditions are considered to cover both single- and two-phase situations. The results show that T p-method is successful for both VLE and LLE, and that T p- and P p-methods are comparable for VLE.