Free Tool
Steel Hardness Conversion Calculator
Enter a value in any hardness scale and instantly see conversions to all others. Based on ASTM E140 standard conversion tables for carbon and alloy steels.
Range: 20 - 68
Range: 0 - 100
Range: 76 - 739
Range: 80 - 940
Range: 25 - 97
Approximate only
1 ksi = 6.895 MPa
Common Reference Points
Conversion Notes
- Approximate conversions only. Hardness conversions between different scales are empirical relationships, not exact mathematical conversions. Actual values can vary depending on the specific steel alloy, its microstructure, and surface condition.
- ASTM E140 standard applies specifically to carbon and alloy steels. Conversions may not be valid for stainless steels, non-ferrous metals, or other materials.
- HRC and HRB overlap region: Around 20 HRC / 97 HRB, both scales can be used. Below 20 HRC, use HRB or Brinell. Above 100 HRB, use Rockwell C.
- Tensile strength estimates above approximately 55 HRC are unreliable and not included in the ASTM E140 tables, as steels at these hardnesses are too brittle for standard tensile testing.
- Brinell values above 450 HB require tungsten carbide ball indenters (HBW). Standard steel ball (HBS) tests are not valid above this limit.
- For critical applications, always perform the actual hardness test on the specific scale required by your specification rather than relying on converted values.
Frequently Asked Questions
HRC (Rockwell C) is the most common hardness scale for hardened steels. It uses a diamond cone indenter with a 150 kgf major load. The scale ranges from 20 to 68 HRC, with higher numbers indicating harder material. Steels below about 20 HRC are too soft for accurate Rockwell C measurement and should be measured on the Rockwell B (HRB) or Brinell (HB) scale instead. HRC is widely specified in engineering drawings, steel standards, and heat treatment specifications.
HRC to HB conversion uses the ASTM E140 standard conversion tables. There is no single formula — the relationship is non-linear. For example, 30 HRC equals approximately 294 HB, 40 HRC equals approximately 371 HB, and 50 HRC equals approximately 481 HB. Values between table data points are found by linear interpolation. These conversions are approximate and can vary depending on the specific steel alloy and its microstructure.
Mild steel (such as S275, EN3, or BS 080M15) typically has a Brinell hardness of about 120-130 HB, which corresponds to approximately 67-70 HRB and 125-135 HV. Mild steel is too soft to measure accurately on the Rockwell C scale. Its approximate tensile strength is around 410-450 MPa (60-65 ksi). Higher-carbon medium steels like EN8 (080M40) are harder at around 200 HB in the normalised condition.
HB (Brinell) uses a 10mm hardened steel or tungsten carbide ball with a 3000 kgf load — ideal for softer steels and castings with coarse grain structures. HV (Vickers) uses a diamond pyramid indenter and works across a very wide hardness range, making it versatile for both soft and hard materials, thin sections, and surface coatings. HRC (Rockwell C) uses a diamond cone with a 150 kgf load and gives a direct reading — it is the fastest test and most commonly specified for hardened and heat-treated steels.
Hardox 400 wear plate has a nominal hardness range of 370-430 HBW (typically around 400 HB), which corresponds to approximately 43 HRC, 392 HV, and around 1250 MPa tensile strength. Hardox 500 has a nominal hardness of 470-530 HBW (typically around 500 HB), corresponding to approximately 51-52 HRC, 530 HV, and around 1760 MPa tensile strength. Both are abrasion-resistant steels manufactured by SSAB and widely used for wear liners, buckets, tippers, and chutes.
Yes, approximate tensile strength can be estimated from hardness values using the ASTM E140 tables. For example, 30 HRC corresponds to roughly 1000 MPa (145 ksi), and 50 HRC corresponds to roughly 1760 MPa (255 ksi). However, these conversions are approximate and apply primarily to carbon and alloy steels. Above about 55 HRC, tensile strength values become unreliable as steels at these hardnesses are very brittle and do not fail in a ductile manner during tensile testing. For accurate tensile data, actual tensile testing should always be performed.