Liquidus projection usually refers to a two-dimensional projection of ternary liquidus univariant lines at constant pressure. The algorithms used in Pandat for the calculation of liquidus projection with isothermal lines and invariant reac- tion equations in a ternary system are presented. These algorithms have been extended to multicomponent liquidus projec- tions and have also been implemented in Pandat. Some examples on ternary and quaternary liquidus projections are pre- sented. The algorithms used in Pandat for the calculation of liquidus projection with isothermal lines and invariant reac- tion equations in a ternary system are presented. These algorithms have been translated into liquid two- dimensional projections of ternary liquidus univariant lines at constant pressure. extended to multicomponent liquidus projec- tions and have also been implemented in Pandat. Some examples on ternary and quaternary liquidus projections are pre- sented.