How to use this calculator
Enter the test force (F) applied by the diamond indenter in kilograms-force, then enter the two diagonal lengths (d1, d2) measured across the resulting square indentation in micrometers. Click Calculate to get the Vickers Hardness Number. Click Clear to reset all fields to the example values.
The Vickers hardness formula
The Vickers hardness test presses a square-based diamond pyramid indenter, with a 136° angle between opposite faces, into a material under a known force. The Vickers Hardness Number is calculated as:
HV = 1.8544 × F / d²
where F is the applied test force in kilograms-force (kgf) and d is the arithmetic mean of the two diagonals of the indentation, measured in millimeters. The constant 1.8544 comes from 2 sin(68°), where 68° is half of the indenter's 136° included angle. HV is conventionally reported without units, or as kgf/mm² — it is written as, for example, "215 HV10" to record both the hardness value and the test force used (10 kgf).
Understanding the inputs
The test force is set by the testing machine, and standardized values include HV1, HV5, HV10, and HV30 (the number is the force in kgf). The two diagonals are measured under a microscope after the indenter is removed — because the indentation is a nearly perfect square, both diagonals should be close in length. This calculator converts the diagonals from micrometers to millimeters internally before applying the formula.
Interpreting the results
The Vickers Hardness card is the primary result. The Mean diagonal card shows the averaged measurement the formula is built on. The Applied force card converts the kgf input to newtons (multiplying by standard gravity, 9.80665) for reference against machines calibrated in SI units. The Diagonal difference card reports how far apart the two measured diagonals are as a percentage of their mean — ASTM E384 flags indentations where the two diagonals differ by more than about 5%, which can indicate a tilted sample or a measurement error.