The Vickers hardness scale (HV): meaning and notation

Written by

Akuracy

2 Nov 20268 min read

The Vickers hardness scale, written as HV, expresses a material’s resistance to indentation under a specified test force. Understanding what the Vickers hardness scale (HV) means requires looking at how the indentation is measured, which test conditions are reported, and why an HV value is not a complete description by itself.

What the Vickers hardness scale (HV) measures

The Vickers hardness scale measures resistance to indentation: a diamond indenter presses into a material, and the resulting impression is measured to determine its hardness. The HV value is not a direct measure of tensile strength, toughness or resistance to every kind of damage.

Hardness is a material property assessed through a defined hardness test. In the Vickers hardness test, a smaller indentation generally corresponds to a higher calculated hardness when the test force and method are held consistent. This makes Vickers hardness useful for comparing materials or regions tested under matching conditions.

However, hardness, strength and toughness describe different behaviours. A hardness value indicates resistance to a local indentation; tensile strength describes resistance to a pulling force, while toughness relates to energy absorbed before fracture. A hard material is not automatically tough, and an HV number alone cannot establish how a part will perform in service.

Vickers testing can be applied to a range of metallic materials and to small areas or localized regions, provided the specimen and method are suitable. For example, a laboratory might use it to compare a surface-treated region with the underlying material. The result applies to the tested location and conditions, not necessarily to every part of a component.

HV is the usual notation for Vickers hardness. The number should be read alongside the test force and other specified conditions rather than as a standalone grade. This distinction matters when comparing a certificate, a production check and results from different laboratories.

How the Vickers test produces an HV value

A Vickers hardness test uses a diamond pyramid indenter, a specified force and measurements of the indentation’s diagonals to calculate an HV value. The resulting number is meaningful only in relation to the method and conditions used.

The indenter and test force

The Vickers indenter has a square-based pyramid shape with a diamond tip. During the hardness test, it is pressed into a prepared surface using a selected test force for a specified period. The force and the indenter’s geometry are part of the test definition.

Test force affects the size of the impression and can influence the reported value, particularly when comparing results taken at different force levels. That is why two HV results should not be treated as directly equivalent just because both use the Vickers method. Check whether the force and applicable procedure match.

The test force should suit the material, the size of the region being examined and the test objective. A small feature may require a different approach from a broad, uniform specimen. The chosen force should follow the relevant test method and laboratory procedure rather than being selected solely for convenience.

Measuring the indentation diagonals

After the force is removed, the two diagonals of the square-shaped impression are measured under suitable magnification. Their average is used with the applied force and the Vickers method’s calculation to determine hardness.

Measuring both diagonals helps account for a mark that is not perfectly symmetrical. If the impression edges are difficult to identify, or if surface preparation leaves scratches and unevenness, the measurements may be less certain. Consistent measurement practice is therefore part of sound hardness testing, not just a matter of reading the machine display.

For instance, if a test mark appears elongated or its corners are unclear, a user should follow the applicable procedure for assessing the impression rather than assume the displayed value is automatically representative. Recording the measurement conditions and following a consistent inspection method makes results easier to review and compare.

Why an HV number needs its test conditions

An HV number without its test conditions is incomplete because force, dwell time, specimen condition and measurement practice can affect how the result should be interpreted. Reporting these details helps another person understand what was tested and whether a comparison is valid.

What to include when reporting Vickers hardness

A useful Vickers hardness record should identify the result and the conditions needed to interpret it. At a minimum, record:

• The measured HV value.
• The applied test force, using the notation required by the applicable method.
• The dwell time when it is specified or relevant to the procedure.
• The test standard or laboratory procedure used.
• The material, specimen identification and test location, where applicable.
• Any relevant preparation or measurement notes required by the procedure.

The exact reporting format should follow the applicable standard and the laboratory’s quality system. A result stated simply as “HV 300,” for example, does not tell the reader which force was used or whether the test followed a specified method. Include enough information for the intended reader to assess the result.

For a quality-control record, it can also be useful to distinguish the individual readings from any summary value and to identify the tested surface or region. These details make it easier to investigate differences between batches, locations or laboratories without assuming the results were produced under identical conditions.

How force and specimen preparation affect results

Test force, surface condition, specimen thickness and measurement practice can all affect the indentation or the reliability of its measurement. Following the method consistently helps reduce avoidable variation and makes comparisons more meaningful.

The test surface should be prepared so that the indentation can be made and measured according to the relevant procedure. Roughness, contamination, scratches or an uneven surface can make the impression’s edges harder to identify. Preparation should suit the material and test objective without changing the region being evaluated in a way that undermines the result.

Specimen thickness and support matter because the indentation should represent the material being tested rather than movement or influence from an unsuitable setup. The required thickness, spacing from edges and spacing between impressions should be checked against the applicable test method. These requirements should not be guessed from an HV value.

Test force should also be selected consistently when comparing readings. If one result uses a different force or preparation method, a difference in HV may not indicate a change in the material alone. When a result is unexpected, review the force, specimen preparation, indenter condition, measurement procedure and test location before drawing conclusions.

How to interpret HV values and conversion limits

An HV value is most useful when compared with results obtained using the same method and suitable conditions. Conversion to another hardness scale is approximate and depends on the material and applicable conversion guidance, so direct testing is preferable when accuracy matters.

Hardness scales use different indenters, forces and measurement principles. A conversion table can provide an estimate for certain materials and ranges, but it does not make one method’s result identical to a direct test using another method. Material type and condition can affect how well a conversion applies.

If a specification requires a particular scale, use that test method where practical rather than relying on a converted value. If conversion is necessary, identify the source or standard used and confirm that it covers the material and hardness range in question. Do not present a converted value as though it were a direct measurement.

This is especially relevant when reviewing records made using different methods. A Vickers result and a Rockwell result may both describe indentation hardness, but the figures are not interchangeable. For a comparison of Rockwell steel results and their limits, see Rockwell hardness scale for steel: selection and limits. For another indentation method, see how Brinell hardness is tested.

Choose a Vickers tester and support for reliable results

Choose a Vickers tester by matching its force range and measurement capability to your specimens and required procedure, then checking calibration arrangements and ongoing technical support. A suitable instrument is one that fits the application and produces results that can be interpreted and maintained consistently.

Before selecting a tester, define the materials, expected hardness range, specimen dimensions, test locations and reporting requirements. Then verify that the machine’s documented capabilities and measurement arrangements fit those needs. Ask how the instrument supports the required test force and how the indentation is measured; do not assume all testers suit every scale of specimen or application.

A practical evaluation checklist includes:

• Does the stated force range cover the tests required by your procedure?
• Can the measurement system resolve and record the impressions needed for your application?
• What calibration process and supporting documentation are available?
• What training is provided for operators, including specimen preparation and result interpretation?
• How are service requests handled, and what is the expected support response process?
• Are maintenance, repair and relevant replacement parts addressed in the service discussion?

These questions help distinguish equipment capability from the conditions required to achieve dependable results. Calibration status alone does not replace correct specimen preparation, trained operation or a consistent procedure. Buyers should also confirm that the delivered configuration matches the agreed specification and that the acceptance checks are understood before installation.

Akuracy offers a Computerized Vickers Hardness Tester, as well as calibration, repair and support services for testing laboratories and industrial quality-control operations. Buyers evaluating a specific application should confirm the required force range, measurement functions, calibration arrangements, operator training and service process for the configuration under consideration.

Recommended next steps

To use the Vickers hardness scale correctly, record the HV result with its force and relevant test conditions, and compare it only with suitable results or references. If you are choosing equipment, define your application and verify the tester’s measurement, calibration and support arrangements.

For an overview of Akuracy’s material-testing equipment and services, visit the Akuracy homepage. When a result affects a formal acceptance decision, consult the applicable test standard and a qualified testing professional for your specific material and procedure.