Calculate Vickers hardness number (HV) from indentation diagonals and applied force. Understand material hardness testing.
Last Updated: 5/6/2026
Load applied by the diamond pyramid indenter (0.2 to 100 kgf typical)
First diagonal of square impression
Second diagonal of square impression
The Vickers hardness test is a micro-indentation hardness measurement technique widely used in materials science and engineering. Unlike the Rockwell test (which measures surface penetration depth), Vickers measures the size of the indentation left by a diamond indenter in the shape of a square-based pyramid with an angle of 136° between opposite faces. When pushed into a material with a known force (typically 1 to 100 kgf), the indenter leaves a small square impression. The hardness number is calculated from the applied load and the area of the indentation, measuring the material's resistance to plastic deformation. The test produces a dimensionless hardness number (HV) that is independent of the load applied—truly hard materials show similar HV values regardless of force, ideal for comparing materials scientifically. Vickers testing excels at measuring very small features, thin coatings, and localized hardness variations, making it invaluable for quality control in aerospace, automotive, and cutting-tool industries.
The calculation uses the formula HV = 1.8544 × F / d², where F is the applied force in kilograms-force (kgf) and d is the average of the two diagonals measured from the indentation (in millimeters). The factor 1.8544 comes from the geometry of the square pyramid: it converts the measured diagonals and applied force into a standardized hardness number. Modern hardness testers include optical systems to measure the indentation diagonals automatically, reducing human error. Hardness values typically range from ~20 HV for soft lead to >1000 HV for carbide or hardened steel. The Vickers scale is continuous and linear, unlike Rockwell, and it is recognized internationally (ISO 6507) as a standard method for hardness measurement, especially in research and precision engineering.
Input the load applied to the diamond indenter in kilograms-force (kgf). Standard forces range from 0.2 kgf (micro-hardness) to 100 kgf (macro-hardness). For typical materials testing, 50 kgf is common.
Using a microscope (typical magnification 400×–1000×), measure both diagonals (d₁ and d₂) of the square indentation left in the material surface. Modern hardness testers do this automatically; manual measurement requires careful optical alignment.
The calculator automatically averages the two diagonals: d = (d₁ + d₂) / 2. This average is used in the hardness formula. Small variations between diagonals indicate slight surface irregularities or non-uniform material properties.
The calculator displays HV (Vickers hardness number, dimensionless). Higher HV values indicate harder materials. Compare your result to reference values for known materials (e.g., ~500 HV for hardened steel, ~200 HV for soft aluminum) to validate your measurement and ensure the test was performed correctly.
Scenario: A technician tests a hardened steel sample using a Vickers indenter with a 50 kgf load. Under the microscope, the indentation diagonals measure d₁ = 0.423 mm and d₂ = 0.425 mm. Calculate the Vickers hardness number.
Vickers measures indentation area (load-independent hardness number); Rockwell measures penetration depth (load-dependent). Vickers is more precise and scientific, useful for research and quality control. Rockwell is faster and suited for production testing. Vickers works on any material; Rockwell has limitations on thin or soft materials.
The indentation may not be perfectly square due to material anisotropy or surface irregularities. Measuring both diagonals (and averaging) reduces error from a single imperfect measurement. A large difference between d₁ and d₂ signals potential problems: bad surface prep, uneven loading, or directional hardness variation.
Approximate conversions exist: 1 HV ≈ 0.0254 HRC (Rockwell C Scale), though these are rough and material-dependent. Use published conversion tables from ASTM E140 for standard materials. Modern software often includes conversion functions, but direct measurement in the desired scale is more accurate.
Vickers is a micro-indentation technique; it measures hardness in a small localized region (thousands of micrometers). Lighter loads (<1 kgf) measure near-surface hardness; heavier loads (50–100 kgf) penetrate deeper, revealing bulk hardness and subsurface properties. It's excellent for mapping hardness gradients in case-hardened or surface-treated parts.
Typical diagonals range 0.1–1.0 mm depending on load and material softness. Light loads (0.2 kgf) on hard steel produce ~0.1 mm impressions; heavy loads (100 kgf) on soft aluminum produce ~1 mm impressions. Smaller impressions allow testing fine microstructures; larger ones reduce measurement error percentage.
Yes, but use light loads (1–10 kgf) to avoid over-penetration or surface pile-up distorting measurements. Pure copper (~200 HV) and soft aluminum (~100 HV) require careful technique and excellent optical measurement systems. Harder alloys are easier to test; soft metals require calibrated equipment with micro-indentation capability.
The surface must be polished smooth (typically 0.1 μm diamond paste on final polish) to allow accurate diagonal measurement under a microscope. Remove scratch marks and oxidation; cleanliness is critical since surface defects affect indentation geometry and measured diagonals. For thin parts, prepare a flat perpendicular surface.
Yes, higher temperatures generally reduce hardness. Steel hardness can drop 5–10% per 100°C above room temperature. Test standards specify room temperature (23°C ± 5°C) for consistency. For elevated-temperature hardness, specialized hot-stage hardness testers are required; results are reported separately to avoid confusion with room-temperature values.