Vickers Hardness Number Calculator - HV Formula and Results

A Vickers hardness number calculator computes the Vickers hardness (HV) of a material from the applied test force and the mean diagonal of the indentation left by a diamond pyramid indenter. The Vickers hardness test is one of the most widely used methods for characterizing material hardness in engineering labs, quality control, and academic research.

Materials engineers, metallurgists, and students use this calculator when they need to convert raw indentation measurements into a standardized hardness value. The Vickers method works for metals, ceramics, and thin coatings because it uses a geometrically similar indenter across all load levels. This vickers hardness number calculator simplifies the process by handling the formula and unit conversions automatically.

Common use cases include reporting hardness from a lab indentation test, comparing material batches against a specification, estimating tensile strength from hardness data when a tensile test is not available, and converting between hardness scales for drawing or certificate review. For comparing Vickers readings with Brinell or Rockwell values, the hardness conversion calculator provides a reference table for steel.

The calculator accepts force in Newtons and mean diagonal in millimeters, then returns the Vickers hardness number in kgf/mm² along with surface area hardness in MPa and an approximate tensile strength. Using this vickers hardness number calculator ensures consistent results across different test conditions and material types.

The Vickers hardness number comes from the ratio of the applied force to the surface area of the indentation. The diamond indenter has a square pyramid shape with a 136° angle between opposite faces. After the test force is removed, you measure the two diagonals of the square indentation and average them. This vickers hardness number calculator uses the standard ISO formula to compute HV from those measurements.

The formula is:

Where F is the applied force in Newtons, α is the indenter face angle (136°), g is the standard gravitational acceleration (9.80665 m/s²), and d is the mean diagonal length in millimeters. The result is expressed in kgf/mm². The vickers hardness number calculator applies this formula directly, so you do not need to manually compute the sine term or handle unit conversions.

According to ISO 6507-1, the Vickers hardness test for metallic materials specifies a diamond pyramid indenter with a 136° face angle and defines the standard test conditions for reporting hardness values. This standard ensures that results from different laboratories remain comparable.

The calculator also computes surface area hardness H in MPa using H = HV × 9.80665, which converts from kgf/mm² to SI units. An estimated tensile strength follows from the rule of thumb σu ≈ H/3 for metallic crystalline materials. These additional outputs make the vickers hardness number calculator useful for materials selection and quality assurance workflows.

A Vickers hardness of 37.82 HV indicates a relatively soft material. For reference, annealed copper typically falls in the 40-100 HV range, while hardened tool steel exceeds 700 HV. The vickers hardness number calculator helps you interpret where your material falls on this scale.

According to Omni Calculator, the Vickers hardness number is calculated as HV = 2F sin(α/2) / (gd²) where α = 136° and g = 9.80665 m/s².

When you need to compute stress from force and area for a different loading geometry, the stress calculator handles normal, tensile, compressive, and shear stress modes.

When indentation causes measurable plastic deformation and you need to convert engineering strain to true strain for material models, the true strain calculator provides the logarithmic conversion.

1. 1 Perform the indentation test: Press the diamond pyramid indenter into the material surface with a known force F for the specified dwell time (typically 10-15 seconds). Record the applied force in Newtons.
2. 2 Measure the diagonals: Using a calibrated microscope, measure both diagonal lengths of the square indentation in millimeters. Record both values.
3. 3 Calculate the mean diagonal: Average the two diagonal measurements to obtain the mean diagonal d. For example, if d1 = 0.502 mm and d2 = 0.498 mm, then d = 0.500 mm.
4. 4 Enter the values: Type the applied force in Newtons and the mean diagonal in millimeters into the calculator fields above.
5. 5 Read the results: The calculator displays the Vickers hardness number HV in kgf/mm², surface area hardness in MPa, and estimated tensile strength in MPa.
6. 6 Report the hardness: Write the result in standard nomenclature: xxxHVyy where xxx is the hardness number and yy is the test force in kgf. For example, 38HV5 means HV = 38 at 5 kgf test force.

A materials lab tests an aluminum alloy specimen with a 50 N force. The microscope reads d1 = 0.502 mm and d2 = 0.498 mm. The mean diagonal is 0.500 mm. Entering F = 50 N and d = 0.5 mm gives HV = 37.82 kgf/mm², surface area hardness = 370.9 MPa, and estimated tensile strength = 123.62 MPa.

For direct tensile testing of the same material, the tension calculator computes engineering stress from load and original cross-section.

• • Standardized hardness reporting: Convert raw indentation measurements into ISO 6507-1 compliant Vickers hardness numbers that can be compared across laboratories and included in material certificates.
• • Tensile strength estimation: When a tensile test is impractical or destructive, the hardness-to-strength relationship provides a non-destructive screening estimate for quality control and material verification.
• • SI unit conversion: Surface area hardness in MPa feeds directly into stress calculations and finite element models without manual unit conversion from kgf/mm².
• • Load range flexibility: The same formula works for macro-hardness tests above 1 kgf and micro-hardness tests below 0.01 kgf, so one calculator covers the full Vickers range.
• • Academic coursework support: Students working through materials science problems can verify hand calculations and build intuition for how force and diagonal affect the hardness result.

• • Surface preparation: The test surface must be flat, clean, and free of oxide scale or contamination. A poorly prepared surface distorts the indentation shape and introduces measurement error in the diagonal reading.
• • Dwell time: Standard Vickers tests hold the force for 10-15 seconds. Shorter dwell times may not allow full plastic deformation, while longer times can cause creep in softer materials, both affecting the final diagonal measurement.
• • Indentation spacing: Adjacent indentations must be spaced far enough apart that their plastic zones do not interact. ISO 6507-1 specifies minimum distances based on diagonal length to avoid work-hardening effects from neighboring tests.
• • Diagonal measurement accuracy: Because the diagonal appears squared in the denominator, a small measurement error produces roughly twice the percentage error in HV. Calibrated microscopes and consistent measurement technique are essential.

Limitations: The tensile strength estimate (σu ≈ H/3) is a rule of thumb for metallic crystalline materials. According to Zhang et al. (2006), the hardness-to-yield-strength ratio varies with material structure, work hardening behavior, and test conditions. Do not use this estimate for design calculations without experimental validation. The Vickers method also assumes homogeneous, isotropic material behavior; anisotropic materials, coatings thinner than the indentation depth, and materials with significant elastic recovery may give misleading hardness values.

When a drawing or specification calls out Rockwell hardness instead of Vickers, the Rockwell hardness conversion calculator converts between HRC, HRA, HRB, HBW, HV, and HK scales.