In this work, the mass and linear thicknesses of AlN and CrN coatings deposited onto silicon substrates by magnetron sputtering were measured, respectively, by a combination of the methods of nondestructive radioactivation analysis on proton beams of the U-120M cyclotron and optical micro-interferometry. It is shown that, at linear thicknesses in the range of 2.2-5.7 μm, the coating density is close to the values for bulk materials AlN (3.26 g / cm3) and CrN (5.9 g / cm3), and the stoichiometry of nitrides is controlled by the parameters of magnetron deposition. The technique can also be used to determine the density of wear-resistant coatings from carbides and metal oxides.