The electrical conductivity of polypropylene/graphite (PP/G) composites and polypropylene/graphite/carbon black (PP/G/CB) composites was investigated in this article. A simulation procedure, which is not limited to any specific parameters (i.e. graphite size and shape), was used to numerically compute the electrical conductivity of the composites. The simulations were carried out using a 2D finite element program based on the digital image analysis. The simulation results were in good agreement with the experimental conductivity values even though there were several limitations in using digital image analysis such as sampling, sample preparation, the quality of the image and the choice of the threshold. The microstructures of the surfaces of the composites were observed using scanning electron microscopy (SEM).