Porosity is a peculiar characteristic of most sintered materials. As to materials for mechanical applications, the degree of porosity can have a strong effect on the levels of some functional characteristics. Causes determining the presence of pores in sintered materials are reviewed. The analysis of the densification mechanism in pressing allows to obtain the corresponding law between applied pressure and porosity. Characteristics of sintered materials which are depending on porosity are distinguished from those which are connected to the lattice structure. Then, the analytical dependence laws between:porosity and conductivity, magnetic properties, UTS., fatigue resistance, rupture elongation, apparent hardness, elastic moduli, surface roughness, hardenability, carburizing depth, hardening depth in induction hardening, properties after steam oxidation treatment are obtained.The achievements fill some gaps still existing in technical literature. The formulae proposed can be applied in the design stage of sintered iron base components.The availability of sound mathematical formulae to be applied in practice is considered a valid support for the further development of P/M applications.