Vickers Hardness Number Calculator

The Vickers hardness test measures a material's resistance to permanent indentation. A diamond indenter shaped as a square-based pyramid is pressed into a prepared surface under a known load. After removing the load, an optical system measures the two diagonals of the square impression. The Vickers Hardness Number, commonly written HV, relates the applied force to the sloping surface area of that indentation. Harder materials generally produce smaller impressions under the same load and therefore have larger HV values. This calculator averages the two diagonal measurements and applies HV = 1.8544 F / d², where F is the test load in kilogram-force and d is the average diagonal length in millimeters. The factor 1.8544 incorporates the geometry of a Vickers indenter, whose angle between opposite faces is 136 degrees. Because diagonal length is squared, measurement errors have a strong influence on the reported hardness. Careful focusing, edge identification, and surface preparation are essential for reliable results. Enter the load in kilogram-force rather than newtons when using the displayed formula. If an instrument reports force in newtons, divide by standard gravity, approximately 9.80665 newtons per kilogram-force, before entry. Enter both diagonals in millimeters. Micrometer readings must be divided by 1,000. The two values should be reasonably close; a large difference can indicate a distorted impression, poor surface finish, specimen movement, anisotropy, or a reading error. Averaging reduces small observational differences but does not repair an invalid test. Vickers testing covers a broad hardness range because the same indenter geometry is used with different forces. Macrohardness tests use larger loads, while microhardness tests use much smaller forces to examine coatings, phases, or thin sections. A reported value should normally include the load designation and dwell conditions, because results can vary with force, specimen thickness, spacing, and material response. The calculator returns the numerical HV ratio but cannot determine whether the indentation met the procedural requirements of a particular standard. For formal quality control, follow the current test method specified by standards such as ASTM E92, ASTM E384, or ISO 6507, as applicable. Ensure the specimen is sufficiently thick, keep indentations away from edges and one another, verify machine calibration, and report appropriate significant figures. This tool is best used to check arithmetic, explore how load and diagonal size affect hardness, and support laboratory calculations after valid measurements have been obtained.