A method determines a performance index of a cooking vessel subjected to a heating power, the index being representative of the capacity of the vessel to distribute the heating power in a homogeneous manner, the vessel including a bottom and a lateral wall furnished with an external face. The method includes a) subjecting the bottom of the vessel to a heating system, b) measuring and recording at regular time intervals the temperature at least three points of predetermined altitude of the external face until the stabilization of at least one of the measured temperatures at each time interval at the level of the at least three points, c) calculating and recording in the course of the time taken for the temperature of the external face to rise, the difference between the maximum temperature and the minimum temperature measured, d) determining the performance index based on the calculations and recordings.