Convert HRC, HRB, Brinell, Vickers and Tensile Strength
Enter a hardness reading on any of 13 scales, or an approximate tensile strength, and get the equivalent Rockwell, Brinell, Vickers, Knoop and superficial values at once. Conversions follow the ASTM E140 and ASTM A370 tables for steel, with a separate table for austenitic stainless. The spec check shows at a glance whether the value meets the hardness limits for common bolt, stud and nut grades.
Where this hardness falls
Spec check
How the converted value compares with the hardness limits in each specification.
Rockwell C hardness conversion chart (HRC 68 to 20)
Approximate equivalents for carbon, alloy and tool steels, plus ferritic and martensitic stainless steels, in the as-forged, annealed, normalized and quenched and tempered conditions. Brinell numbers in parentheses are outside the range recommended for Brinell testing. Tensile strength is approximate and listed from 59 HRC down.
| HRC | HV | HBW | HK | HRA | HRD | HR15N | HR30N | HR45N | Tensile, approx. |
|---|---|---|---|---|---|---|---|---|---|
| 68 | 940 | — | 920 | 85.6 | 76.9 | 93.2 | 84.4 | 75.4 | — |
| 67 | 900 | — | 895 | 85.0 | 76.1 | 92.9 | 83.6 | 74.2 | — |
| 66 | 865 | — | 870 | 84.5 | 75.4 | 92.5 | 82.8 | 73.3 | — |
| 65 | 832 | (739) | 846 | 83.9 | 74.5 | 92.2 | 81.9 | 72.0 | — |
| 64 | 800 | (722) | 822 | 83.4 | 73.8 | 91.8 | 81.1 | 71.0 | — |
| 63 | 772 | (705) | 799 | 82.8 | 73.0 | 91.4 | 80.1 | 69.9 | — |
| 62 | 746 | (688) | 776 | 82.3 | 72.2 | 91.1 | 79.3 | 68.8 | — |
| 61 | 720 | (670) | 754 | 81.8 | 71.5 | 90.7 | 78.4 | 67.7 | — |
| 60 | 697 | (654) | 732 | 81.2 | 70.7 | 90.2 | 77.5 | 66.6 | — |
| 59 | 674 | 634 | 710 | 80.7 | 69.9 | 89.8 | 76.6 | 65.5 | 351 ksi (2420 MPa) |
| 58 | 653 | 615 | 690 | 80.1 | 69.2 | 89.3 | 75.7 | 64.3 | 338 ksi (2330 MPa) |
| 57 | 633 | 595 | 670 | 79.6 | 68.5 | 88.9 | 74.8 | 63.2 | 325 ksi (2240 MPa) |
| 56 | 613 | 577 | 650 | 79.0 | 67.7 | 88.3 | 73.9 | 62.0 | 313 ksi (2160 MPa) |
| 55 | 595 | 560 | 630 | 78.5 | 66.9 | 87.9 | 73.0 | 60.9 | 301 ksi (2070 MPa) |
| 54 | 577 | 543 | 612 | 78.0 | 66.1 | 87.4 | 72.0 | 59.8 | 292 ksi (2010 MPa) |
| 53 | 560 | 525 | 594 | 77.4 | 65.4 | 86.9 | 71.2 | 58.6 | 283 ksi (1950 MPa) |
| 52 | 544 | 512 | 576 | 76.8 | 64.6 | 86.4 | 70.2 | 57.4 | 273 ksi (1880 MPa) |
| 51 | 528 | 496 | 558 | 76.3 | 63.8 | 85.9 | 69.4 | 56.1 | 264 ksi (1820 MPa) |
| 50 | 513 | 481 | 542 | 75.9 | 63.1 | 85.5 | 68.5 | 55.0 | 255 ksi (1760 MPa) |
| 49 | 498 | 469 | 526 | 75.2 | 62.1 | 85.0 | 67.6 | 53.8 | 246 ksi (1700 MPa) |
| 48 | 484 | 455 | 510 | 74.7 | 61.4 | 84.5 | 66.7 | 52.5 | 238 ksi (1640 MPa) |
| 47 | 471 | 443 | 495 | 74.1 | 60.8 | 83.9 | 65.8 | 51.4 | 229 ksi (1580 MPa) |
| 46 | 458 | 432 | 480 | 73.6 | 60.0 | 83.5 | 64.8 | 50.3 | 221 ksi (1520 MPa) |
| 45 | 446 | 421 | 466 | 73.1 | 59.2 | 83.0 | 64.0 | 49.0 | 215 ksi (1480 MPa) |
| 44 | 434 | 409 | 452 | 72.5 | 58.5 | 82.5 | 63.1 | 47.8 | 208 ksi (1430 MPa) |
| 43 | 423 | 400 | 438 | 72.0 | 57.7 | 82.0 | 62.2 | 46.7 | 201 ksi (1390 MPa) |
| 42 | 412 | 390 | 426 | 71.5 | 56.9 | 81.5 | 61.3 | 45.5 | 194 ksi (1340 MPa) |
| 41 | 402 | 381 | 414 | 70.9 | 56.2 | 80.9 | 60.4 | 44.3 | 188 ksi (1300 MPa) |
| 40 | 392 | 371 | 402 | 70.4 | 55.4 | 80.4 | 59.5 | 43.1 | 182 ksi (1250 MPa) |
| 39 | 382 | 362 | 391 | 69.9 | 54.6 | 79.9 | 58.6 | 41.9 | 177 ksi (1220 MPa) |
| 38 | 372 | 353 | 380 | 69.4 | 53.8 | 79.4 | 57.7 | 40.8 | 171 ksi (1180 MPa) |
| 37 | 363 | 344 | 370 | 68.9 | 53.1 | 78.8 | 56.8 | 39.6 | 166 ksi (1140 MPa) |
| 36 | 354 | 336 | 360 | 68.4 | 52.3 | 78.3 | 55.9 | 38.4 | 161 ksi (1110 MPa) |
| 35 | 345 | 327 | 351 | 67.9 | 51.5 | 77.7 | 55.0 | 37.2 | 156 ksi (1080 MPa) |
| 34 | 336 | 319 | 342 | 67.4 | 50.8 | 77.2 | 54.2 | 36.1 | 152 ksi (1050 MPa) |
| 33 | 327 | 311 | 334 | 66.8 | 50.0 | 76.6 | 53.3 | 34.9 | 149 ksi (1030 MPa) |
| 32 | 318 | 301 | 326 | 66.3 | 49.2 | 76.1 | 52.1 | 33.7 | 146 ksi (1010 MPa) |
| 31 | 310 | 294 | 318 | 65.8 | 48.4 | 75.6 | 51.3 | 32.5 | 141 ksi (970 MPa) |
| 30 | 302 | 286 | 311 | 65.3 | 47.7 | 75.0 | 50.4 | 31.3 | 138 ksi (950 MPa) |
| 29 | 294 | 279 | 304 | 64.8 | 47.0 | 74.5 | 49.5 | 30.1 | 135 ksi (930 MPa) |
| 28 | 286 | 271 | 297 | 64.3 | 46.1 | 73.9 | 48.6 | 28.9 | 131 ksi (900 MPa) |
| 27 | 279 | 264 | 290 | 63.8 | 45.2 | 73.3 | 47.7 | 27.8 | 128 ksi (880 MPa) |
| 26 | 272 | 258 | 284 | 63.3 | 44.6 | 72.8 | 46.8 | 26.7 | 125 ksi (860 MPa) |
| 25 | 266 | 253 | 278 | 62.8 | 43.8 | 72.2 | 45.9 | 25.5 | 123 ksi (850 MPa) |
| 24 | 260 | 247 | 272 | 62.4 | 43.1 | 71.6 | 45.0 | 24.3 | 119 ksi (820 MPa) |
| 23 | 254 | 243 | 266 | 62.0 | 42.1 | 71.0 | 44.0 | 23.1 | 117 ksi (810 MPa) |
| 22 | 248 | 237 | 261 | 61.5 | 41.6 | 70.5 | 43.2 | 22.0 | 115 ksi (790 MPa) |
| 21 | 243 | 231 | 256 | 61.0 | 40.9 | 69.9 | 42.3 | 20.7 | 112 ksi (770 MPa) |
| 20 | 238 | 226 | 251 | 60.5 | 40.1 | 69.4 | 41.5 | 19.6 | 110 ksi (760 MPa) |
Rockwell B hardness conversion chart (HRB 100 to 30)
Approximate equivalents for softer, non-austenitic steels. Tensile strength is approximate and listed from 100 HRB down to 65 HRB.
| HRB | HV | HB | HK | HRA | HRF | HR15T | HR30T | HR45T | Tensile, approx. |
|---|---|---|---|---|---|---|---|---|---|
| 100 | 240 | 240 | 251 | 61.5 | — | 93.1 | 83.1 | 72.9 | 116 ksi (800 MPa) |
| 99 | 234 | 234 | 246 | 60.9 | — | 92.8 | 82.5 | 71.9 | 114 ksi (785 MPa) |
| 98 | 228 | 228 | 241 | 60.2 | — | 92.5 | 81.8 | 70.9 | 109 ksi (750 MPa) |
| 97 | 222 | 222 | 236 | 59.5 | — | 92.1 | 81.1 | 69.9 | 104 ksi (715 MPa) |
| 96 | 216 | 216 | 231 | 58.9 | — | 91.8 | 80.4 | 68.9 | 102 ksi (705 MPa) |
| 95 | 210 | 210 | 226 | 58.3 | — | 91.5 | 79.8 | 67.9 | 100 ksi (690 MPa) |
| 94 | 205 | 205 | 221 | 57.6 | — | 91.2 | 79.1 | 66.9 | 98 ksi (675 MPa) |
| 93 | 200 | 200 | 216 | 57.0 | — | 90.8 | 78.4 | 65.9 | 94 ksi (650 MPa) |
| 92 | 195 | 195 | 211 | 56.4 | — | 90.5 | 77.8 | 64.8 | 92 ksi (635 MPa) |
| 91 | 190 | 190 | 206 | 55.8 | — | 90.2 | 77.1 | 63.8 | 90 ksi (620 MPa) |
| 90 | 185 | 185 | 201 | 55.2 | — | 89.9 | 76.4 | 62.8 | 89 ksi (615 MPa) |
| 89 | 180 | 180 | 196 | 54.6 | — | 89.5 | 75.8 | 61.8 | 88 ksi (605 MPa) |
| 88 | 176 | 176 | 192 | 54.0 | — | 89.2 | 75.1 | 60.8 | 86 ksi (590 MPa) |
| 87 | 172 | 172 | 188 | 53.4 | — | 88.9 | 74.4 | 59.8 | 84 ksi (580 MPa) |
| 86 | 169 | 169 | 184 | 52.8 | — | 88.6 | 73.8 | 58.8 | 83 ksi (570 MPa) |
| 85 | 165 | 165 | 180 | 52.3 | — | 88.2 | 73.1 | 57.8 | 82 ksi (565 MPa) |
| 84 | 162 | 162 | 176 | 51.7 | — | 87.9 | 72.4 | 56.8 | 81 ksi (560 MPa) |
| 83 | 159 | 159 | 173 | 51.1 | — | 87.6 | 71.8 | 55.8 | 80 ksi (550 MPa) |
| 82 | 156 | 156 | 170 | 50.6 | — | 87.3 | 71.1 | 54.8 | 77 ksi (530 MPa) |
| 81 | 153 | 153 | 167 | 50.0 | — | 86.9 | 70.4 | 53.8 | 73 ksi (505 MPa) |
| 80 | 150 | 150 | 164 | 49.5 | — | 86.6 | 69.7 | 52.8 | 72 ksi (495 MPa) |
| 79 | 147 | 147 | 161 | 48.9 | — | 86.3 | 69.1 | 51.8 | 70 ksi (485 MPa) |
| 78 | 144 | 144 | 158 | 48.4 | — | 86.0 | 68.4 | 50.8 | 69 ksi (475 MPa) |
| 77 | 141 | 141 | 155 | 47.9 | — | 85.6 | 67.7 | 49.8 | 68 ksi (470 MPa) |
| 76 | 139 | 139 | 152 | 47.3 | — | 85.3 | 67.1 | 48.8 | 67 ksi (460 MPa) |
| 75 | 137 | 137 | 150 | 46.8 | 99.6 | 85.0 | 66.4 | 47.8 | 66 ksi (455 MPa) |
| 74 | 135 | 135 | 147 | 46.3 | 99.1 | 84.7 | 65.7 | 46.8 | 65 ksi (450 MPa) |
| 73 | 132 | 132 | 145 | 45.8 | 98.5 | 84.3 | 65.1 | 45.8 | 64 ksi (440 MPa) |
| 72 | 130 | 130 | 143 | 45.3 | 98.0 | 84.0 | 64.4 | 44.8 | 63 ksi (435 MPa) |
| 71 | 127 | 127 | 141 | 44.8 | 97.4 | 83.7 | 63.7 | 43.8 | 62 ksi (425 MPa) |
| 70 | 125 | 125 | 139 | 44.3 | 96.8 | 83.4 | 63.1 | 42.8 | 61 ksi (420 MPa) |
| 69 | 123 | 123 | 137 | 43.8 | 96.2 | 83.0 | 62.4 | 41.8 | 60 ksi (415 MPa) |
| 68 | 121 | 121 | 135 | 43.3 | 95.6 | 82.7 | 61.7 | 40.8 | 59 ksi (405 MPa) |
| 67 | 119 | 119 | 133 | 42.8 | 95.1 | 82.4 | 61.0 | 39.8 | 58 ksi (400 MPa) |
| 66 | 117 | 117 | 131 | 42.3 | 94.5 | 82.1 | 60.4 | 38.7 | 57 ksi (395 MPa) |
| 65 | 116 | 116 | 129 | 41.8 | 93.9 | 81.8 | 59.7 | 37.7 | 56 ksi (385 MPa) |
| 64 | 114 | 114 | 127 | 41.4 | 93.4 | 81.4 | 59.0 | 36.7 | — |
| 63 | 112 | 112 | 125 | 40.9 | 92.8 | 81.1 | 58.4 | 35.7 | — |
| 62 | 110 | 110 | 124 | 40.4 | 92.2 | 80.8 | 57.7 | 34.7 | — |
| 61 | 108 | 108 | 122 | 40.0 | 91.7 | 80.5 | 57.0 | 33.7 | — |
| 60 | 107 | 107 | 120 | 39.5 | 91.1 | 80.1 | 56.4 | 32.7 | — |
| 59 | 106 | 106 | 118 | 39.0 | 90.5 | 79.8 | 55.7 | 31.7 | — |
| 58 | 104 | 104 | 117 | 38.6 | 90.0 | 79.5 | 55.0 | 30.7 | — |
| 57 | 103 | 103 | 115 | 38.1 | 89.4 | 79.2 | 54.4 | 29.7 | — |
| 56 | 101 | 101 | 114 | 37.7 | 88.8 | 78.8 | 53.7 | 28.7 | — |
| 55 | 100 | 100 | 112 | 37.2 | 88.2 | 78.5 | 53.0 | 27.7 | — |
| 54 | — | — | 111 | 36.8 | 87.7 | 78.2 | 52.4 | 26.7 | — |
| 53 | — | — | 110 | 36.3 | 87.1 | 77.9 | 51.7 | 25.7 | — |
| 52 | — | — | 109 | 35.9 | 86.5 | 77.5 | 51.0 | 24.7 | — |
| 51 | — | — | 108 | 35.5 | 86.0 | 77.2 | 50.3 | 23.7 | — |
| 50 | — | — | 107 | 35.0 | 85.4 | 76.9 | 49.7 | 22.7 | — |
| 49 | — | — | 106 | 34.6 | 84.8 | 76.6 | 49.0 | 21.7 | — |
| 48 | — | — | 105 | 34.1 | 84.3 | 76.2 | 48.3 | 20.7 | — |
| 47 | — | — | 104 | 33.7 | 83.7 | 75.9 | 47.7 | 19.7 | — |
| 46 | — | — | 103 | 33.3 | 83.1 | 75.6 | 47.0 | 18.7 | — |
| 45 | — | — | 102 | 32.9 | 82.6 | 75.3 | 46.3 | 17.7 | — |
| 44 | — | — | 101 | 32.4 | 82.0 | 74.9 | 45.7 | 16.7 | — |
| 43 | — | — | 100 | 32.0 | 81.4 | 74.6 | 45.0 | 15.7 | — |
| 42 | — | — | 99 | 31.6 | 80.8 | 74.3 | 44.3 | 14.7 | — |
| 41 | — | — | 98 | 31.2 | 80.3 | 74.0 | 43.7 | 13.6 | — |
| 40 | — | — | 97 | 30.7 | 79.7 | 73.6 | 43.0 | 12.6 | — |
| 39 | — | — | 96 | 30.3 | 79.1 | 73.3 | 42.3 | 11.6 | — |
| 38 | — | — | 95 | 29.9 | 78.6 | 73.0 | 41.6 | 10.6 | — |
| 37 | — | — | 94 | 29.5 | 78.0 | 72.7 | 41.0 | 9.6 | — |
| 36 | — | — | 93 | 29.1 | 77.4 | 72.3 | 40.3 | 8.6 | — |
| 35 | — | — | 92 | 28.7 | 76.9 | 72.0 | 39.6 | 7.6 | — |
| 34 | — | — | 91 | 28.2 | 76.3 | 71.7 | 39.0 | 6.6 | — |
| 33 | — | — | 90 | 27.8 | 75.7 | 71.4 | 38.3 | 5.6 | — |
| 32 | — | — | 89 | 27.4 | 75.2 | 71.0 | 37.6 | 4.6 | — |
| 31 | — | — | 88 | 27.0 | 74.6 | 70.7 | 37.0 | 3.6 | — |
| 30 | — | — | 87 | 26.6 | 74.0 | 70.4 | 36.3 | 2.6 | — |
Austenitic stainless steel hardness conversion (Brinell to Rockwell B)
For annealed austenitic stainless plate such as 304 and 316. The steel tables above do not apply to austenitic grades, and no tensile estimate is given.
| HRB | HB | HRB | HB |
|---|---|---|---|
| 100 | 256 | 79 | 150 |
| 99 | 248 | 78 | 147 |
| 98 | 240 | 77 | 144 |
| 97 | 233 | 76 | 142 |
| 96 | 226 | 75 | 139 |
| 95 | 219 | 74 | 137 |
| 94 | 213 | 73 | 135 |
| 93 | 207 | 72 | 132 |
| 92 | 202 | 71 | 130 |
| 91 | 197 | 70 | 128 |
| 90 | 192 | 69 | 126 |
| 89 | 187 | 68 | 124 |
| 88 | 183 | 67 | 122 |
| 87 | 178 | 66 | 120 |
| 86 | 174 | 65 | 118 |
| 85 | 170 | 64 | 116 |
| 84 | 167 | 63 | 114 |
| 83 | 163 | 62 | 113 |
| 82 | 160 | 61 | 111 |
| 81 | 156 | 60 | 110 |
| 80 | 153 |
Hardness limits for bolts, studs and nuts
Hardness requirements from the governing specifications. Select a grade for its strength, material and equivalents in the material cross-reference.
Using hardness conversions correctly
- Conversions are approximate. Each test method measures a different mix of material properties, so a converted number is an estimate. Convert specification limits rather than test data wherever possible, and test on the scale the specification requires when acceptance depends on it.
- Use the right table. The steel tables cover carbon, alloy and tool steels and ferritic and martensitic stainless steels. They do not apply to austenitic stainless steel, nonferrous metals or hard drawn wire.
- Report the original reading. Show the measured value and scale with any converted number, for example 353 HBW (38 HRC).
- Tensile strength from hardness is an estimate for through-hardened steel. It does not replace a tension test, and it does not apply to case-hardened, cold-worked or austenitic material.
- Certification. Every Patriot Bolt order ships with a certificate of conformance; material test reports (MTRs) with measured hardness are available when requested on the order.
Frequently asked questions
How do I convert HRC to Brinell?
For carbon and alloy steel, look up the Rockwell C number in the conversion table and read across to the Brinell column, or enter it in the calculator above. For example, 35 HRC is about 327 HBW and 22 HRC is about 237 HBW. Brinell numbers above about 60 HRC are outside the range recommended for Brinell testing and are shown in parentheses.
How do I convert Rockwell hardness to tensile strength?
For through-hardened carbon and alloy steel, ASTM A370 gives an approximate tensile strength for each Rockwell C number from 20 to 59 and each Rockwell B number from 65 to 100. A quick rule of thumb is that tensile strength in ksi is roughly half the Brinell number. The estimate is not a substitute for a tension test and should not be used for austenitic stainless steel or hard drawn wire.
What is 22 HRC in Brinell and Vickers?
22 HRC converts to about 237 HBW and 248 HV for non-austenitic steel. 22 HRC is the general hardness limit for carbon and low-alloy steel in sour service under NACE MR0175 / ISO 15156-2.
What hardness is ASTM A193 B7?
A193 B7 studs are limited to 35 HRC (321 HBW) maximum. B7M, the sour service version, is limited to 235 HBW (99 HRB) maximum, and both are paired with A194 heavy hex nuts: 2H for B7 and 2HM for B7M.
When should I use Rockwell B instead of Rockwell C?
Rockwell C is used for hardened steel from about 20 to 68 HRC. Below 20 HRC, readings become unreliable and the softer Rockwell B scale (ball indenter) is used up to 100 HRB. The two scales overlap near 20 HRC and 100 HRB.
Can hardness conversion tables be used for stainless steel?
The standard steel tables apply to ferritic and martensitic stainless steels such as 410 and 17-4PH, but not to austenitic grades such as 304 and 316. Austenitic stainless steel has its own Brinell to Rockwell B table for annealed plate, which this calculator uses when you choose the austenitic option.
How should a converted hardness value be reported?
Report the converted value with the original measurement and scale in parentheses, for example 353 HBW (38 HRC). Converted values are approximate and should be rounded to no more significant digits than the table provides.
Are hardness conversions exact?
No. Each hardness test measures a different combination of material properties, so conversions are approximate and depend on alloy, heat treatment and microstructure. Convert specification limits rather than test results wherever possible, and test on the scale the specification calls for when acceptance depends on it.
Related tools and references
- Material and Grade Cross-Reference – ASTM, SAE, ISO, EN and UNS bolting equivalents
- Metallurgy Selector – chemical and temperature compatibility for bolting materials
- Sour Service Bolting Quick Reference – hardness-controlled grades for H2S service
- Thread Designer – UN, metric and NPT thread limits, wires and CNC passes
- Bolted Joint Calculator (VDI 2230) – joint stiffness, preload loss and safety factors for yield, separation and slip