Equivalent hardness values across Brinell (HB), Vickers (HV), Rockwell (HRC, HRB, HRA), and approximate tensile strength for carbon and low-alloy steels. Values cross-checked against ASTM E140-12 Table 1 and ISO 18265:2013 Annex A. Conversions are approximate — see the notes below before quoting a number on a drawing.
| Scale | Indenter / Load | Useful range | Typical use |
|---|---|---|---|
| HB (Brinell) | 10 mm ball, 3000 kgf | ~80–650 HB | Castings, forgings, large sections, raw stock |
| HV (Vickers) | Diamond pyramid, 1–50 kgf | ~5–3000 HV | Thin parts, case depth, surface treatments, lab work |
| HRC (Rockwell C) | Diamond cone, 150 kgf | 20–70 HRC | Hardened steel, tool steel, heat-treated parts |
| HRB (Rockwell B) | 1/16″ ball, 100 kgf | 0–100 HRB | Soft steel, mild steel, annealed brass, aluminum |
| HRA (Rockwell A) | Diamond cone, 60 kgf | 20–88 HRA | Cemented carbide, thin hardened layers, very hard materials |
| HR15N / 30N / 45N (Superficial) | Diamond cone, 15/30/45 kgf | Various | Thin-sheet hardened surfaces, nitrided cases, coatings |
Approximate equivalent hardness values for carbon and low-alloy steels (ASTM E140-12 Table 1 & ISO 18265:2013 Annex A). To read: pick a row in your known scale, the other columns are the approximate equivalents.
| HV | HB | HRC | HRA | HRB | Tensile (MPa, approx.) |
|---|---|---|---|---|---|
| 940 | — | 68.0 | 85.6 | — | — |
| 900 | — | 67.0 | 85.0 | — | — |
| 865 | 739 | 65.0 | 84.1 | — | — |
| 766 | 653 | 62.0 | 82.6 | — | — |
| 694 | 600 | 60.0 | 81.2 | — | — |
| 613 | 534 | 56.0 | 79.0 | — | — |
| 547 | 482 | 52.0 | 76.7 | — | 1740 |
| 505 | 461 | 50.0 | 75.5 | — | 1620 |
| 449 | 415 | 46.0 | 73.3 | — | 1480 |
| 406 | 375 | 42.0 | 71.0 | — | 1350 |
| 353 | 327 | 38.0 | 68.5 | — | 1180 |
| 316 | 293 | 34.0 | 65.8 | — | 1065 |
| 286 | 269 | 30.0 | 62.8 | — | 970 |
| 258 | 241 | 25.0 | 59.8 | 100 | 870 |
| 240 | 227 | 22.0 | 57.3 | 100 | 815 |
| 226 | 217 | 20.0 | 55.2 | 97 | 770 |
| 210 | 200 | (17.5) | 52.0 | 94 | 710 |
| 199 | 192 | (15.5) | 50.0 | 92 | 680 |
| 183 | 179 | (11.0) | 46.5 | 89 | 620 |
| 156 | 156 | — | — | 83 | 530 |
| 129 | 131 | — | — | 74 | 440 |
| 105 | 107 | — | — | 62 | 360 |
| 90 | 95 | — | — | 52 | 310 |
Parenthesized HRC values (e.g. (17.5), (15.5), (11.0)) lie outside the reliable range of the Rockwell C scale (per ISO 18265 §5) and are listed only as estimates — do not cite them on drawings. Use HRB or HV instead.
For carbon and low-alloy steels in the as-quenched-and-tempered condition, tensile strength (MPa) can be approximated from Brinell hardness:
| # | Mistake | What goes wrong | Fix |
|---|---|---|---|
| 1 | Reporting HRC below 20 | Below 20 HRC the diamond cone barely penetrates; small reading errors mean huge hardness swings | Switch to HRB, HB, or HV below 20 HRC |
| 2 | Using the carbon-steel table for stainless | Austenitic stainless (304, 316) work-hardens differently; carbon-steel conversions under-read by 5–15% | Use ASTM E140 Table 2 (austenitic) or measure directly |
| 3 | Interpolating between rows | Hardness is not linear across scales; mid-points don’t preserve the conversion relationship | Pick the nearest row and report that value |
| 4 | Trusting tensile-from-hardness for design | The 3.45×HB rule has ±15% real-world scatter depending on microstructure | Use it for estimate only; for cert values do a real tensile test |
| 5 | Mixing HB (steel ball) and HBW (tungsten carbide ball) above 450 HB | Steel balls deform above ~450 HB; ISO requires tungsten carbide (HBW) there | Always use HBW above 450 HB; cite HBW explicitly |
| 6 | Comparing HRC and HRA as if linearly related | HRC and HRA use the same indenter but different loads; conversion is non-linear | Use the conversion table; never divide or multiply directly |
Around 20 HRC. Below that, the Rockwell C diamond cone doesn’t penetrate enough to give a stable reading, and ASTM E140 / ISO 18265 list those values only in parentheses as estimates. For softer steel (annealed, normalized, or low-carbon), use HRB, HB, or HV.
Only as a rough estimate, and only for carbon and low-alloy steels in the quenched-and-tempered condition. The rule σUTS (MPa) ≈ 3.45 × HB holds within about ±15% in the 150–450 HB range. For austenitic stainless, tool steels, or cast iron, use a different relation — and for any value that goes on a certificate or PPAP, run an actual tensile test per ISO 6892-1 or ASTM E8.
Two reasons. First, Brinell uses a spherical indenter and Vickers a pyramid — the deformation field is different, so the conversion drifts. Second, above ~450 HB the traditional steel ball starts to deform, so ISO requires a tungsten carbide ball (HBW). HV stays accurate to much higher values, which is why ISO 18265 uses it as the reference scale.
No. They use the same diamond cone indenter but at different loads (150 kgf for HRC vs 60 kgf for HRA). The relationship is non-linear; you must use the conversion table. HRC is for hardened steel in the 20–70 range; HRA is preferred for very hard materials like cemented carbide and thin hardened layers.
Cite the scale your heat-treat supplier will actually measure — usually HRC for hardened parts (42–48 HRC is typical for through-hardened steel) or HB for annealed / normalized parts. Best practice: cite a range in two scales (e.g., “42–48 HRC ≈ 419–490 HV”) so a supplier using either method can self-verify.
ASTM and ISO both caution that conversions are approximate. Uncertainty isn’t tabulated in the standards because it varies by material, microstructure, and scale pair. Expect ±1–2 HRC of scatter for steels in the mid-range (30–50 HRC), more at the extremes. Critical parts should be measured in the scale cited on the drawing.
We test every heat-treated batch in-house (Rockwell, Brinell, Vickers) and report the actual measured value — not a conversion — on your material cert.
Request a Quote