Derivation, validity testing and usage in practice of the powder compaction Eq.P = P(0.)exp(-K.p(n)) is presented. P is the porosity at pressure p, P-0 the porosity at p = 0, parameters K and it represent the synergistically acting compaction parameters. The relationship between K and n, In(K) = 12952-73349.n or K = 3.6517.exp(-7.3349.n), was found on the basis of cold die-compaction testing of 205 various metal powder mixes. This analysis enables calculation of additional criteria characterizing the compressibility of various metal powders. To facilitate the analysis, a graphical processing of the relationship between the relative porosity P/P-0 of the compact, p and n is also presented. In practice, its use could provide a rapid assessment of the compressibility behaviour of various metal powders. (C) 2017 Elsevier B.V. All rights reserved.