6 Nov 2026
6 min read
The Vickers hardness test principle is to press a diamond indenter into a prepared surface with a specified force, measure the two diagonals of the resulting square-shaped impression, and calculate hardness from the force and indentation size. The method can be used on metals and coatings; the selected force, specimen condition, and test standard determine whether a particular setup is suitable.
What is the principle of the Vickers hardness test? The quick answer
Vickers hardness is calculated from the applied force and the average length of the indentation’s two diagonals: a smaller impression under the same force indicates a higher hardness value.
The indenter is a square-based diamond pyramid. After it is pressed into the material and removed, the impression is viewed and its diagonals are measured. The Vickers hardness number, commonly written as HV, is calculated using the force and the mean diagonal length.
This principle makes the method useful across different scales of hardness testing, provided the force and indentation can be selected and measured appropriately. The relevant test method, ISO 6507-1:2023 for Vickers testing, covers metallic materials and coatings, including the force ranges and indentation sizes within its scope.
A Vickers test differs from a Brinell hardness test, which uses a ball indenter and measures the diameter of a rounded impression. A Brinell hardness tester may suit a different material, surface, or measurement scale; the choice depends on the specimen and the test requirement, not simply on the method’s name.
What is the principle of the Vickers hardness test? The step-by-step process
A valid result depends on a sequence: prepare a suitable surface, apply the specified force through the correct indenter, measure the impression, and record the conditions alongside the result.
Prepare the right setup
Start by confirming the applicable test method, the material, the specimen’s thickness and shape, and the force required for the measurement. Select a Vickers hardness tester and diamond indenter suitable for those requirements. Do not substitute a ball indenter from a Brinell hardness tester: it creates a different impression and belongs to a different test method.
Prepare a flat, stable test surface so the impression can be seen and measured clearly. Remove surface contamination and finish the area as needed for reliable optical measurement, while avoiding preparation that changes the material’s condition at the test surface. Support the specimen firmly; movement or poor contact can affect the impression.
Before testing, check that the indenter and measuring system are appropriate for the method and that the equipment’s calibration status meets your laboratory’s requirements. Agree on the force and reporting format before collecting results. If the test is for a specification or quality-control decision, follow that specification rather than choosing conditions solely for convenience.
Follow the core process
Place the specimen so the prepared area is stable and aligned with the indenter. Bring the indenter into contact and apply the specified force according to the equipment’s operating procedure. Maintain the force for the required dwell time, then remove it as instructed.
Next, locate the indentation using the measurement system. Measure both diagonals of the square-shaped impression, from corner to opposite corner. Use their arithmetic mean as the diagonal length for the calculation. If the corners are unclear, the surface is uneven, or the image is distorted, do not treat an uncertain reading as precise; review the preparation and measurement conditions.
The Vickers hardness calculation is commonly expressed as:
HV = 1.8544 × F / d²
Here, F is the applied force in kilogram-force, and d is the mean diagonal length in millimetres. The reported notation must identify the force and dwell conditions required by the applicable method or laboratory procedure. Do not compare values without checking that their test conditions are comparable.
Check whether it is working
Check the impression before accepting the value: it should be sufficiently clear for both diagonals to be identified and measured. Record the individual diagonal readings, not just the calculated hardness result. If repeated impressions are part of the procedure, assess their consistency against the laboratory’s acceptance criteria rather than assuming that one reading represents the whole material.
A useful review asks whether the result is plausible for the material and test location, whether the measurement image is clear, and whether the applied force and equipment status were recorded correctly. A surprising result is a reason to check the setup, specimen surface, indenter condition, and measurement—not to change the force after the fact without documenting the change.
For standards-based testing, confirm that the selected conditions fall within the method’s scope. The ISO Vickers test method specifies force ranges and indentation sizes for the materials it covers. A machine’s displayed result alone does not establish that the full procedure matched the required method.
Avoid the common mistakes
Common errors include testing an unstable specimen, measuring a poorly defined indentation, using the wrong indenter, and recording HV without the conditions needed to interpret it. Surface preparation can also affect the reading if it alters or obscures the area being tested.
Keep the force, dwell time, material condition, and measurement method consistent when comparing results. Make sure the diagonals are measured across the actual impression corners, not across scratches or surface features. If the two diagonals differ markedly or the impression is irregular, investigate alignment, surface quality, and the specimen’s structure before reporting the value.
Do not treat a Vickers result as interchangeable with a Brinell hardness test result simply because both describe hardness. The indenter geometry and measurement differ. For a separate explanation of the ball-indenter method, see how Brinell hardness is tested.
When to adjust your Vickers test approach
Change the setup or method when the specimen’s thickness, curvature, size, surface condition, or required measurement makes a clear, representative indentation difficult to obtain.
Thin samples need particular care: the indentation must not be influenced by the specimen’s support or by the opposite surface. Curved surfaces can make seating and diagonal measurement difficult, while very small samples may not provide enough suitable area for the required impressions and spacing. Do not assume a standard flat-specimen procedure applies unchanged to these cases.
For thin, curved, or very small specimens, check the applicable test method and laboratory procedure before selecting a force or test location. Consider whether the surface can be prepared without changing the property being measured, and whether the resulting impression can be measured reliably. If not, a different test method or specimen preparation may be more suitable.
A Vickers test can also be useful for small measurement areas, but “small” does not remove the need for a clearly measurable impression or appropriate spacing from edges and other impressions. The method’s scope and the specimen’s geometry should guide the choice. Consult a qualified testing professional for advice on a specific specimen or acceptance decision.
Recommended next steps
Use the planned test conditions and specimen geometry to decide whether the Vickers method can produce a readable, representative indentation.
- Identify the material, test location, specimen thickness, curvature, and applicable test requirement.
- Confirm that the selected Vickers indenter, force, dwell conditions, and measurement system suit the specimen and required method.
- Prepare a representative surface and verify that the specimen can be supported without movement during indentation.
- Make a trial impression, inspect both diagonals, and repeat the setup check if the corners are unclear or the result appears irregular.
- Record the force, dwell conditions, both diagonal measurements, calculated HV value, specimen identification, and equipment calibration status.
- Compare results only when the method and test conditions are sufficiently consistent; use the laboratory’s applicable acceptance criteria.
- If Brinell testing is under consideration instead, review the distinct Brinell hardness calculation steps and confirm that method fits the material and requirement.