This document specifies the Knoop hardness test method for metallic materials for test forces from 0,009 807 N to 19,613 N. This document specifies Knoop hardness tests for length of the long diagonal ≥0,020 mm. Using this method to determine the Knoop hardness from smaller indentations is outside the scope of this document as results would suffer from large uncertainties due to the limitations of optical measurement and imperfections in tip geometry. The Knoop hardness test specified in this document is also applicable for metallic and other inorganic coatings including electrodeposited coatings, autocatalytic coatings, sprayed coatings and anodic coatings on aluminium. This document is applicable to measurements normal to the coated surface and to measurements on cross-sections, provided that the characteristics of the coating (smoothness, thickness, etc.) permit accurate readings of the diagonal of the indentation. This document is not applicable for coatings with thickness less than 0,007 mm when testing normal to the coating surface. This document is not applicable for coatings with thickness less than 0,020 mm when testing a cross-section of the coating. ISO 14577-1 can be used for the determination of hardness from smaller indentations. A periodic verification method is specified for routine checking of the testing machine in service by the user.