Deformation and transport mechanisms of matter, which intervene in the powder densification process by hot isostatic pressing (HIP), are very complicated to put into equation form. Their contribution to densification depends on powder characteristics, their configuration in aggregates, and the used HIP cycle parameters (temperature, pressure, and time). In this work, we have envisaged modifications that seemed to us necessary to bring to the previous simulations, so that their predictions will be related to experiment. New equations were established to evaluate the efficient pressure and the contributions of different mechanisms. The obtained results are used for the construction of densification diagrams by the HIP of copper, nickel, and tungsten powders and to the comparison with the experimental data. The comparative tables, between theoretical results and experimental data, were established for tin and lead. The simulation predictions are in good agreement with experimental results.