Hardness Conversion Calculator for Steel — Brinell, Rockwell & Vickers
Convert measured HBW, HRC, HRB or HV hardness to approximate equivalent scales for non-austenitic carbon and low-alloy steels using tabulated reference correlations.
Enter the known values and review the calculated result
Input parameters
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Hardness conversion
Results
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Method, application and limitations
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Formula and calculation method
Hardness conversion method
This hardness conversion calculator converts a measured hardness value between Brinell (HBW), Rockwell C (HRC), Rockwell B (HRB), and Vickers (HV). The implemented correlations are intended for non-austenitic carbon and low-alloy steels.
The calculator does not use a single hardness conversion factor or a universal analytical equation. It uses selected steel hardness reference points and, when the entered value lies between two supported points, performs linear interpolation.
Linear interpolation
For an entered hardness value x located between two reference values x1 and x2, the interpolation fraction is:
f = (x − x1) / (x2 − x1)
The equivalent value on a target hardness scale is then:
y = y1 + f(y2 − y1)
where y1 and y2 are the target-scale values from the same two reference rows.
If the entered hardness exactly matches a reference point, the corresponding chart value is used directly. Interpolated equivalent values are rounded to the nearest whole hardness number. The originally entered hardness value is preserved without conversion.
Supported input ranges
| Scale | Supported input range | Calculator notation |
|---|---|---|
| Brinell | 111–650 | HBW / HB |
| Rockwell C | 20–68 | HRC |
| Rockwell B | 65–100 | HRB |
| Vickers | 114–940 | HV |
No extrapolation is performed. If a value is outside the supported range, the calculation is rejected. If either bounding reference row has no value for a requested target scale, that equivalent is intentionally left unavailable instead of being estimated across the missing data.
Brinell equivalents above approximately 650 HBW are also omitted because the implemented engineering reference treats that as the practical upper limit for the Brinell ball-hardness comparison used by this calculator.
When to use this calculator
When to use this hardness conversion calculator
Use this calculator when a hardness value for a non-austenitic carbon or low-alloy steel is available in one supported scale and an approximate equivalent is needed in another.
Typical applications include:
- converting Brinell hardness to Rockwell C, including HB or HBW to HRC;
- converting Rockwell C hardness to approximate Brinell or Vickers values;
- converting Vickers hardness to Rockwell C or Brinell where the reference data overlap;
- comparing HRB and HRC values where both scales are supported by the reference rows;
- cross-checking hardness values reported on drawings, material records, laboratory reports, or supplier documentation;
- making preliminary engineering comparisons when different sources use different hardness scales.
Select the scale in which the hardness was actually measured, enter the measured value, and calculate. The result shows the available HBW/HB, HRC, HRB, and HV equivalents together with the conversion method used.
When not to use it
This tool is not a universal hardness converter. It does not convert Mohs, Shore, Knoop, Leeb, or other hardness scales. It does not calculate tensile strength, identify a material grade, determine heat-treatment condition, or perform a hardness test.
Converted hardness values should not replace a direct test when a drawing, specification, inspection procedure, or acceptance criterion requires a particular hardness scale. In those cases, test the component directly using the required method and scale.
How to interpret the result
How to interpret the converted hardness values
The entered hardness value is the measured value supplied by the user. Values shown on the other scales are approximate equivalent hardness values derived from the implemented steel reference correlation.
The calculator reports one of two conversion methods:
- Reference chart value — the entered value exactly matches an implemented reference point.
- Linear interpolation between reference points — the entered value lies between two reference points and the equivalent is interpolated.
A missing equivalent does not mean that the material has no hardness on that scale. It means that the current reference data do not support a conversion for that interval, or that the resulting Brinell equivalent would exceed the calculator's approximately 650 HBW limit.
Inputs outside 111–650 HBW, 20–68 HRC, 65–100 HRB, or 114–940 HV produce an invalid result because extrapolation is prohibited.
This calculator does not produce a PASS/FAIL material verdict, safety factor, utilization ratio, allowable hardness limit, or acceptance decision. A successful conversion only means that an approximate equivalent could be obtained within the implemented reference range.
Calculation example
Example: convert 400 HBW to Rockwell C and Vickers
Suppose a non-austenitic steel has a measured hardness of 400 HBW. We want approximate equivalent values in HRC and HV.
1. Reference points
The measured value lies between these two implemented reference rows:
| HBW | HV | HRC | HRB |
|---|---|---|---|
| 378 | 392 | 40 | Unavailable |
| 429 | 446 | 45 | Unavailable |
2. Calculate the interpolation fraction
f = (400 − 378) / (429 − 378)
f = 22 / 51 = 0.4314
3. Convert HBW to HRC
HRC = 40 + 0.4314 × (45 − 40)
HRC = 42.16 ≈ 42
4. Convert HBW to HV
HV = 392 + 0.4314 × (446 − 392)
HV = 415.29 ≈ 415
Result
- Measured: 400 HBW
- Rockwell C equivalent: approximately 42 HRC
- Vickers equivalent: approximately 415 HV
- Rockwell B equivalent: unavailable for this reference interval
The HRC and HV values are interpolated engineering equivalents, not new hardness measurements. If HRC or HV is required for inspection or acceptance, the material should be tested directly on the required scale.
Assumptions and limitations
Assumptions and limitations
- The implemented reference is intended for non-austenitic carbon and low-alloy steels.
- The input is assumed to be a valid measured hardness value on the selected HBW/HB, HRC, HRB, or HV scale.
- Equivalent values are approximate correlations, not direct measurements on the target scales.
- Linear interpolation is performed only between adjacent supported reference points.
- No extrapolation beyond the supported input ranges is permitted.
- No target value is calculated when the relevant bounding rows contain missing reference data for that scale.
- Converted equivalents are rounded to whole hardness numbers; the output does not represent additional measurement precision.
- HBW equivalents above approximately 650 are intentionally omitted by the implemented method.
- The calculator does not model measurement uncertainty, test-machine accuracy, specimen geometry, surface preparation, indenter condition, or test-load effects.
- The calculator does not convert hardness to tensile strength and does not support hardness scales other than HBW/HB, HRC, HRB, and HV.
- The implemented table is not a verbatim implementation of ASTM E140 or ISO 18265.
- For specification limits, inspection, certification, or acceptance testing, use a direct hardness test in the required scale and follow the governing test procedure or standard.
References
Reference data
The conversion anchors used by this calculator are selected values from the PACE Technologies steel hardness conversion chart for Brinell, Vickers, Rockwell C, and Rockwell B hardness.
The calculator uses those selected reference values together with the interpolation, range-control, rounding, and missing-correlation logic implemented in the EngineersCalc calculation code.
Applicable standards
Related hardness conversion standards
- ASTM E140 — Standard Hardness Conversion Tables for Metals.
- ISO 18265 — Metallic materials — Conversion of hardness values.
These standards are relevant technical references for hardness conversion, but this calculator does not reproduce either standard verbatim and does not claim compliance with their complete procedures, tables, material groups, or applicability requirements.