A modified graphical-statistical method for shape factor estimation has been developed and used to estimate the permeability of a perfusive particle as an example. The shape factor was evaluated by calculating the average cross-sectional area for diffusion and the average flow path line length separately. According to this method, a perfusive particle with a sealing surface length ratio, L-S, of 0.04, i.e. a contact length of the perfusive particle on the walls of the test cell tube to the perfusive particle diameter of 0.04, would have a shape factor of 1.25pia. Then, the graphical-statistical method and the geometrical method were used to propose an expression to evaluate the shape factor of any perfusive particle with a sealing surface length ratio of L-S and a radius of a. Finally, the shape factor approach was compared with the CFD numerical simulation approach of Pfeiffer et al. [AlChE J. 42 (1996) 932], and excellent agreement between the two approaches has been demonstrated.