<p>In this paper, five laws proposed to describe the influence of porosity on the effective conductivity (both electrical and thermal) of porous materials, which include a single microstructural parameter, are analyzed. These five laws are as follows: (1) the linear law with threshold, (2) the power law without threshold (Archie’s law), (3) the power law with threshold (percolation law), (4) the exponential law without threshold (decay law), and (5) the exponential law with threshold (Mooney-type law). These laws are discussed and derived from statistical reasoning (taken from the field of Stereology) or from probabilistic reasoning (taken from the field of risk analysis). The five laws are contrasted with the experimental values of electrical and thermal conductivities measured on metallic samples with different porosity, obtained by cold pressing and furnace sintering of four elementary powders (2 of iron, nickel, and aluminum). The study carried out allows to conclude that all the laws analyzed provide satisfactory agreements, but the percolation law is slightly superior to the others, since the values of its microstructural parameter remain within the uncertainty range to support a coherent physical interpretation, which is not the case for the other laws. Finally, the work also addresses the variability with porosity of the Wiedemann–Franz law, finding that it holds reasonably valid for low porosities, but not for higher porosities, which has been justified as a result of the different influence that the oxide layers of the metal powder particles exert on the electrical and thermal conductivities.</p> Graphical Abstract <p></p>