The heat transfer coefficient at the metal-mould interface of a unidirectional solidification system was calculated by an algorithm that uses the whole domain method for the inverse solution to the heat conduction differential equation with phase change. Experimental curves of temperature as a function of time, collected during solidification of Cu-8%Sn alloys subject to four different conditions, were used as input to the algorithm. Accordingly, the heat transfer coefficient at the metal-mould interface was obtained for those conditions. The estimated heat transfer coefficient values are in good agreement with the ones published in the literature.