Al-based alloys were one of the first material types to which thermodynamic phase diagram calculations were applied. Since then improvements in modelling and the increase in computing power has enabled very accurate predictions to be made for phase equilibria in real multicomponent alloys. By JMatPro’s property models a complete set of physical and mechanical properties can be calculated. The present paper describes a general methodology to calculate properties such as the fraction solid transformed, enthalpy, specific heat (Cp) etc. for multi-component alloys.