Hardness scales
- HRC, Rockwell C: diamond cone, for hardened and tempered steels, from about 20 to 68 HRC.
- HRB, Rockwell B: ball, for mild steels and non-ferrous metals.
- HV, Vickers: diamond pyramid, covers the whole range and is used for thin layers too.
- HB, Brinell: large ball, for soft or raw material, castings and forgings. Not used above about 450–650 HB.
How accurate the conversion is
The scales measure different things, so conversion is always approximate: the table holds for carbon and alloy steels, not for austenitic stainless steels, cast irons or non-ferrous metals. Tensile strength derived from hardness is a ballpark figure. If a drawing asks for 58 HRC, acceptance is tested in HRC.
Values in brackets
In the chart, values in brackets are outside the normal range of the scale: for example HB above 59 HRC or HRB above 24 HRC. They are given for reference, but in those ranges another scale is used.
Hardness conversion chart (steels)
| HRC | HV | HB | HRA | HRB | Rm (MPa) |
|---|---|---|---|---|---|
| 68 | 940 | — | 85.6 | — | — |
| 67 | 900 | — | 85 | — | — |
| 66 | 865 | — | 84.5 | — | — |
| 65 | 832 | (739) | 83.9 | — | — |
| 64 | 800 | (722) | 83.4 | — | — |
| 63 | 772 | (705) | 82.8 | — | — |
| 62 | 746 | (688) | 82.3 | — | — |
| 61 | 720 | (670) | 81.8 | — | — |
| 60 | 697 | (654) | 81.2 | — | — |
| 59 | 674 | (634) | 80.7 | — | — |
| 58 | 653 | 615 | 80.1 | — | — |
| 57 | 633 | 595 | 79.6 | — | — |
| 56 | 613 | 577 | 79 | — | — |
| 55 | 595 | 560 | 78.5 | — | 2075 |
| 54 | 577 | 543 | 78 | — | 2015 |
| 53 | 560 | 525 | 77.4 | — | 1950 |
| 52 | 544 | 512 | 76.8 | — | 1880 |
| 51 | 528 | 496 | 76.3 | — | 1820 |
| 50 | 513 | 481 | 75.9 | — | 1760 |
| 49 | 498 | 469 | 75.2 | — | 1695 |
| 48 | 484 | 455 | 74.7 | — | 1635 |
| 47 | 471 | 443 | 74.1 | — | 1580 |
| 46 | 458 | 432 | 73.6 | — | 1530 |
| 45 | 446 | 421 | 73.1 | — | 1480 |
| 44 | 434 | 409 | 72.5 | — | 1435 |
| 43 | 423 | 400 | 72 | — | 1385 |
| 42 | 412 | 390 | 71.5 | — | 1340 |
| 41 | 402 | 381 | 70.9 | — | 1295 |
| 40 | 392 | 371 | 70.4 | — | 1250 |
| 39 | 382 | 362 | 69.9 | — | 1215 |
| 38 | 372 | 353 | 69.4 | — | 1180 |
| 37 | 363 | 344 | 68.9 | — | 1160 |
| 36 | 354 | 336 | 68.4 | (109) | 1115 |
| 35 | 345 | 327 | 67.9 | (108.5) | 1080 |
| 34 | 336 | 319 | 67.4 | (108) | 1055 |
| 33 | 327 | 311 | 66.8 | (107.5) | 1025 |
| 32 | 318 | 301 | 66.3 | (107) | 1000 |
| 31 | 310 | 294 | 65.8 | (106) | 980 |
| 30 | 302 | 286 | 65.3 | (105.5) | 950 |
| 29 | 294 | 279 | 64.7 | (104.5) | 930 |
| 28 | 286 | 271 | 64.3 | (104) | 910 |
| 27 | 279 | 264 | 63.8 | (103) | 880 |
| 26 | 272 | 258 | 63.3 | (102.5) | 860 |
| 25 | 266 | 253 | 62.8 | (101.5) | 840 |
| 24 | 260 | 247 | 62.4 | (101) | 825 |
| 23 | 254 | 243 | 62 | 100 | 805 |
| 22 | 248 | 237 | 61.5 | 99 | 785 |
| 21 | 243 | 231 | 61 | 98.5 | 770 |
| 20 | 238 | 226 | 60.5 | 97.8 | 760 |
| (18) | 230 | 219 | — | 96.7 | 730 |
| (16) | 222 | 212 | — | 95.5 | 705 |
| (14) | 213 | 203 | — | 93.9 | 675 |
| (12) | 204 | 194 | — | 92.3 | 650 |
| (10) | 196 | 187 | — | 90.7 | 620 |
| (8) | 188 | 179 | — | 89.5 | 600 |
| (6) | 180 | 171 | — | 87.1 | 580 |
| (4) | 173 | 165 | — | 85.5 | 550 |
| (2) | 166 | 158 | — | 83.5 | 530 |
| (0) | 160 | 152 | — | 81.7 | 515 |
Steels. HB with a carbide ball. In brackets, values outside the normal range of the scale. Rm is approximate.