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Hardness Conversion Chart

Rockwell C & B, Vickers, Brinell, and approximate tensile strength — converted per ASTM E140.

True Precision Machining
Dual-scale hardness bar, drawn to scale and linear in Rockwell C: a sectioned steel bar with HRC graduations 20, 30, 40, 50, 60, and 65 on top and the equivalent Vickers values 240, 302, 392, 513, 697, and 832 HV under each graduation. Red markers above the bar locate mild steel below 20 HRC, prehard 4140 at 28 to 32, 17-4PH H900 at 40 to 44, hardened tool steel at 60 to 62, and a file near 65. Equal 10-point HRC steps stretch from 62 HV at the soft end to 184 HV at the hard end. MILD STEEL <20 HRC 17-4PH H900 40–44 HRC FILE ~65 HRC 4140 PREHARD 28–32 HRC HARDENED TOOL STEEL 60–62 HRC 20 240 30 302 40 392 50 513 60 697 65 832 HRC HV 10 HRC = 62 HV 10 HRC = 184 HV EQUAL HRC STEPS STRETCH IN HV → ONE HARDNESS — TWO SCALES Conversions per ASTM E140 (steel) — approximate by definition. Spec ONE scale on the drawing; convert for reference only.
Rockwell Vickers Brinell Approx. tensile · steel
HRC HRB HV HBW UTS ksi UTS MPa
68 — 940 — — —
65 — 832 739 — —
62 — 746 688 — —
60 — 697 654 — —
58 — 653 615 — —
56 — 613 577 — —
54 — 577 543 292 2013
52 — 544 512 273 1882
50 — 513 481 255 1758
48 — 484 455 238 1641
46 — 458 432 221 1524
44 — 434 409 208 1434
42 — 411 388 193 1331
40 — 392 371 182 1255
38 — 372 353 171 1179
36 — 354 336 161 1110
34 — 336 319 151 1041
32 — 318 301 143 986
30 — 302 286 136 938
28 — 286 271 129 889
26 — 273 258 123 848
24 — 261 247 117 807
22 — 250 237 112 772
20 100 240 226 107 738
— 98 228 228 102 703
— 95 210 210 98 676
— 92 195 195 93 641
— 90 185 185 90 621
— 86 169 169 86 593
— 80 150 150 81 558
— 75 137 137 — —
— 70 125 125 — —
— 60 107 107 — —
— 50 93 93 — —

Key: bold = primary scales (HRC · HRB · HV)  ·  — = outside that scale’s usable range  ·  UTS = estimate from hardness, steel only

HRC — Rockwell C, diamond cone / 150 kgf. Hardened steel ≥ 20 HRC (tool steel, hardened 4140/4340, 17-4PH H900–H1075).

HRB — Rockwell B, 1/16″ ball / 100 kgf. Annealed steel, brass, aluminum bronze, hard plastics. Above ~100 HRB switch to HRC.

HV — Vickers, diamond pyramid / variable load. One scale from soft aluminum to carbide; thin coatings and case-depth work.

HBW — Brinell, 10 mm tungsten-carbide ball / 3000 kgf for steel. Large indent averages non-uniform material — castings, forgings.

Conversions per ASTM E140 for steel; approximate and dependent on indenter, load, and dwell time. UTS columns per ASTM A370 Table 3 / SAE J417 for non-austenitic steel (the quick rule of thumb ≈ 500 × HBW psi runs a few percent high of the table below ~40 HRC and several percent low above ~45 HRC) — estimates only, never a substitute for an actual tensile test. — in the UTS columns = outside the published correlation, ~HB 156–555 (above ~55 HRC steels fail brittle; no tensile is defined). Non-steel conversions are not transferable; use material-specific tables. For the interactive comparator and indenter notes, see the full hardness conversion reference.

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trueprecisionmachining.com · 805-964-4545 · Buellton, CA · AS9100 / ISO 9001 / ITAR
Approximate conversions for steel per ASTM E140 — verify against material-specific data for non-steel or design-critical work. · September 2026