An approximate hardness conversion calculator for steel
This hardness conversion calculator converts between Rockwell C (HRC), Rockwell B (HRB), Vickers (HV), Brinell (HB) and an estimated tensile strength for carbon and low-alloy steels — for example HV to HRC, HB to HRC or HRB to HB — and draws an approximate hardness conversion chart you can download.
Be clear about what it is. The referee conversions are the tables in ASTM E140 and ISO 18265. Those standards are copyrighted, so this tool does not reproduce them. Instead it uses a handful of published empirical formulas, each named in the working, and shows two independent estimates where they exist so you can see the spread. Expect differences of a few points of HRC or roughly ±5–10% in HB and strength from the tabulated values.
Use it for quick estimates, homework and sanity checks — not for certificates, acceptance or failure analysis. Hardness conversions depend on the material, its heat treatment and cold work. Stainless steels, cast irons, aluminium, copper alloys and surface-hardened parts behave differently, and the formulas here do not apply to them.
How to use the Hardness Conversion Calculator
- Pick the scale you measured in Convert from and type the reading.
- Pick the scale you need in Convert to; all the other scales appear underneath.
- Choose MPa or ksi for strength. Use Swap to reverse the conversion.
- Check the working table for which relation produced each number and its valid range.
- Scroll to the chart for HRC 20–68 and HRB 40–100, or download it as CSV.
Hardness Conversion Calculator features
Five scales
HRC, HRB, HV, HB and tensile strength, converted through Vickers.
Two opinions
Brinell and tensile strength each come from two independent published relations.
Ranges enforced
Values outside a formula’s range are shown as “—” with a note.
Computed chart
An approximate chart from the same formulas, with CSV download.
Sources named
Every row of the working names the relation it used.
The formulas used
- HRC ↔ HV: HV = (223 × HRC + 14,500) ÷ (100 − HRC), and HRC = (100 × HV − 14,500) ÷ (223 + HV), for 20–68 HRC. This is the rational-function form published by H. Qvarnström (Journal of Heat Treating, 1989). It gives 248.8 HV at 22 HRC, matching the 22 HRC ≈ 248 HV equivalence widely used for sour-service limits.
- HB ≈ 0.95 × HV: the Brinell–Vickers relation of the former British Standard BS 860:1967, as cited by TWI. It works best for softer steels.
- HRB → HB: HB = 7,300 ÷ (130 − HRB) for 40–100 HRB, and a second HB estimate from HRC, from V. E. Lysaght’s Indentation Hardness Testing (1949), quoted to about ±10%.
- Tensile and yield strength: TS = −99.8 + 3.734 × HV and YS = −90.7 + 2.876 × HV in MPa, from E. J. Pavlina and C. J. Van Tyne’s 2008 regression over more than 150 steels (valid about 129–592 HV for tensile). Lysaght’s 490–515 × HB psi is shown as a cross-check.
Worked example: 50 HRC
50 HRC gives HV = (223 × 50 + 14,500) ÷ 50 = 513 HV. Brinell is about 0.95 × 513 = 487 HB, while Lysaght’s HRC formula gives 490 HB. Tensile strength is about −99.8 + 3.734 × 513 = 1,816 MPa (263 ksi), and yield strength about 1,385 MPa. A standard table will differ slightly; for acceptance, test in the scale the drawing specifies.
Related calculators
Pick machining speeds for the hardness you found with the cutting speed calculator, estimate stock weight with the steel weight calculator, and convert stress units with the pressure converter (1 MPa = 1 N/mm²).
Hardness Conversion Calculator FAQ
How do I convert HV to HRC?
Use HRC = (100 × HV − 14,500) ÷ (223 + HV) for steels between about 240 and 925 HV. 400 HV is about 40.9 HRC. Below 20 HRC the C scale is not used.
How do I convert HB to HRC?
Convert Brinell to Vickers with HV ≈ HB ÷ 0.95, then Vickers to HRC. 300 HB is about 316 HV, or roughly 32 HRC. Treat this as approximate.
Is there a free hardness conversion chart?
The chart under the calculator is computed from published formulas and can be downloaded as CSV. The official tables are in ASTM E140 and ISO 18265, which you can buy from ASTM or ISO.
Can hardness predict tensile strength?
For plain carbon and low-alloy steels, roughly: tensile strength in MPa is about 3.7 × HV − 100 over 129–592 HV. It does not apply to austenitic stainless or non-ferrous metals.
Why does the hardness conversion calculator give a range?
Different relations were fitted to different data. Showing two estimates makes the uncertainty visible; neither replaces a measurement in the required scale.
Does it work for aluminium or stainless steel?
No. Austenitic stainless steel, cast iron and non-ferrous alloys need their own conversion tables.