Rockwell Hardness Conversion Calculator
Two-way conversion between Rockwell C, Rockwell B, Rockwell A, Vickers (HV), and Brinell (HB), interpolated from the empirical ASTM E140 tables for non-austenitic steels. Includes an inline conversion chart and the full reference table.
Converter
Conversion chart
Curves are drawn directly from the curated table points. The dot marks your input after conversion through Vickers HV as the pivot scale.
How the conversion works
- No formula. Hardness conversion is empirical: this tool looks up the published ASTM E140 table rows and linearly interpolates between adjacent rows. There is no analytic equation behind the numbers.
- HV is the pivot. Every conversion goes from your scale to Vickers HV, then from HV to each target scale. Example: 60 HRC becomes 697 HV, and 697 HV becomes 81.2 HRA and (bracketed) 654 HB.
- Round trips are consistent. Converting 45.5 HRC to HV gives 452 HV, and converting 452 HV back gives 45.5 HRC, within interpolation tolerance.
- No extrapolation. Inputs outside the published ranges (20–68 HRC, 55–100 HRB, 60.5–85.6 HRA, 100–940 HV, 100–739 HB) are rejected instead of guessed.
Scope boundary: what this tool is and is not
This tool converts hardness numbers between HRC, HRB, HRA, HV, and HB using ASTM E140 Table 1 (Rockwell C range) and Table 2 (Rockwell B range) for non-austenitic steels.
This tool does not:
- Measure hardness. It only re-expresses a reading you already took.
- Apply to austenitic stainless steel, cast iron, or non-ferrous alloys. Those materials have their own separate ASTM E140 tables with different numbers.
- Estimate tensile strength, which is a separate correlation with its own limits.
- Produce exact equivalents. Converted values are approximations by definition.
Engineering disclaimer
Converted hardness values are approximate and material-dependent. ASTM E140 advises that conversions be applied primarily to specification limits established by agreement, and that conversion of test data be avoided whenever possible. When a value matters for acceptance, safety, or certification, test the material directly on the required scale. Always report the original measured value and scale alongside any converted number.
Full ASTM E140 reference table
HB is the carbide-ball (HBW) column, 10 mm ball, 3000 kgf. Values for HRC 60–65 are shown in brackets in ASTM E140 itself as practical approximations outside the strict Brinell definition range. No HB is published above HRC 65. All values apply to non-austenitic steels.
Frequently asked questions
What does this Rockwell hardness conversion calculator do?
It converts a hardness number between five common scales, Rockwell C (HRC), Rockwell B (HRB), Rockwell A (HRA), Vickers (HV), and Brinell (HB), using linear interpolation between the published data points of ASTM E140, the standard hardness conversion tables for metals.
How accurate are hardness conversions?
Every conversion is an approximation. ASTM E140 states that converting from one hardness scale to another is only an approximate process because the different tests do not measure exactly the same combination of material properties, so a converted value should never be treated as equal to a direct measurement.
What is ASTM E140?
ASTM E140 is the standard titled Standard Hardness Conversion Tables for Metals. It publishes empirically determined conversion tables between Brinell, Vickers, Rockwell, superficial Rockwell, Knoop, scleroscope, and Leeb hardness, including Table 1 for the Rockwell C range and Table 2 for the Rockwell B range of non-austenitic steels, which are the tables curated into this tool.
How do I convert HRC to HV?
Enter your HRC value and read the Vickers result. For example, 60 HRC converts to 697 HV and 40 HRC converts to 392 HV. Values between table rows are linearly interpolated, so 44.5 HRC gives 440 HV.
How do I convert HRB to HB?
Enter your HRB value and read the Brinell result. For example, 80 HRB converts to 150 HV and 150 HB. Note that some unofficial charts print different numbers, but these are the values published in ASTM E140 Table 2.
When should I use HRC instead of HRB?
Use the Rockwell C scale for harder steels, roughly 20 to 68 HRC. Use the Rockwell B scale for softer materials, from about 55 to 100 HRB. Readings above 100 HRB or below 20 HRC are outside the defined range of those scales, so switch scales instead of converting an out-of-range reading.
Which materials do these conversions apply to?
The tables used here apply to non-austenitic steels, including carbon, alloy, and tool steels in homogeneous conditions. They must not be applied to austenitic stainless steel, cast iron, or non-ferrous alloys, which have their own separate conversion tables in ASTM E140.
What is the difference between HBW and HBS?
HBW is Brinell hardness measured with a tungsten carbide ball indenter and HBS with a hardened steel ball, both commonly with a 10 mm ball and 3000 kgf force. This tool uses the HBW carbide-ball column from ASTM E140 Table 1, which is the modern reference column.
Why do different hardness charts disagree slightly?
Most disagreements come from rounding, from mixing the steel-ball and carbide-ball Brinell columns, or from copying errors in unofficial charts. This tool uses the published ASTM E140 table values directly, including the bracketed Brinell values the standard itself marks as practical approximations for HRC 60 to 65.
What is the Rockwell A scale used for?
The Rockwell A scale uses a diamond cone indenter with a lighter 60 kgf major load, so it is used for thin hardened materials, shallow case-hardened layers, and very hard thin stock where the heavier C-scale load would punch through or be affected by the anvil.
Can I convert hardness to tensile strength?
Not with this tool. Tensile strength is estimated from Brinell hardness with rough correlations such as UTS in MPa being about 3.45 times HB, but that is a separate approximation with its own limits, so it is deliberately outside the scope of this converter.
Should I report the original measurement with a converted value?
Yes. ASTM E140 recommends reporting the converted number together with the original measured value and scale, for example writing 392 HV converted from 40 HRC, so anyone reading the result knows it is a conversion and not a direct Vickers test.
Why does the tool refuse values outside the table range?
Because the tables are empirical, there is no valid formula to extend them. Extrapolating beyond the published range would invent data, so the tool rejects out-of-range inputs instead of guessing.
Is this calculator a substitute for hardness testing?
No. It is an engineering reference for interpreting existing readings, checking specifications, and comparing materials. When a value matters for acceptance, safety, or certification, test the material directly on the required scale instead of converting.
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