The processing line and technique were developed for producing materials from 316L steel fibers 12 and 30 μm in diameter as sheets with a porosity of 50–80% and a thickness of 0.5–10.5 mm. Model concepts of pore shape in sintered metallic fiber materials were used to derive three dependences of the mean pore size of these materials on their porosity and the starting fiber diameter. Comparisons of the mean pore sizes determined experimentally with standard methods and calculated by Valeeva’s equations indicate that the calculated results are highly reliable. This allows predicting the properties of metallic fiber materials with adequate accuracy without additional costs for the production of prototypes, process adjustments, or equipment for experimental determination of the mean pore size.