This free hardness conversion calculator from HAGUE FASTENERS LIMITED converts Rockwell C (HRC), Rockwell B (HRB), Vickers (HV) and Brinell (HB) hardness readings and gives an approximate tensile strength in MPa, ksi and UK tons per square inch. Type a value, choose its scale, and every other scale updates as you type.
Hardness converter
Based on the conversion tables of ISO 18265 (DIN 50150) for unalloyed and low-alloy steels and cast steel. Brinell taken as 0.95 × Vickers. Not valid for austenitic stainless steels, nickel alloys, non-ferrous metals or cold-worked material, where conversions differ. Hardness to tensile strength conversion has more scatter than conversion between hardness scales.
Guidance only. Results are approximate and for initial guidance. They are not a substitute for the governing standard, specification or drawing, or for testing. HAGUE FASTENERS LIMITED accepts no liability for decisions made using these tools. Always check critical values against the relevant standard. © 2026 HAGUE FASTENERS LIMITED.
How to use the hardness converter
- Enter your hardness reading or tensile strength in the Value box.
- Choose the scale the reading was taken on.
- Read the equivalent values on every other scale. The scale you entered is outlined in gold.
The converter uses the conversion tables of ISO 18265 (formerly DIN 50150) for unalloyed and low-alloy steels and cast steel, with straight-line interpolation between table points. Brinell is taken as 0.95 times Vickers, as in those tables.
Hardness limits you will meet on fastener specifications
- ASTM A193 B7 and B16 studs, and ASTM A320 L7: 35 HRC maximum.
- Sour service grades B7M and L7M (NACE MR0175 / ISO 15156): 235 HB (99 HRB) maximum.
- ISO 898-1 property class 10.9: 32 to 39 HRC. Property class 12.9: 39 to 44 HRC.
Always check the hardness requirement against the current issue of the specification you are working to.
Frequently asked questions
How accurate is a hardness conversion?
Conversions between hardness scales are empirical, so they are approximate. Results depend on the material, its heat treatment and its condition. Where a specification calls for a hardness on one scale, test on that scale. Converting hardness to tensile strength has more scatter again, so treat it as an estimate only.
Can I use this for stainless steel or nickel alloys?
No. These tables are for carbon and low-alloy steels. Austenitic stainless steels, nickel alloys such as Inconel and Monel, and non-ferrous metals follow different relationships, and cold-worked material can differ too. Ask us if you need help with these materials.
Why is Rockwell C blank for soft materials?
The Rockwell C scale is not used below about 20 HRC. For softer steels use Rockwell B or Brinell.
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