Hardness converter
Convert between Rockwell, Brinell, Vickers and tensile strength. Based on the conversion table for unalloyed and low-alloy steels, with the full table for reference.
Table range: 20.3 to 68.0 HRC
Applies according to ISO 18265 Table A.1 to unalloyed and low-alloy steels and cast steel, not to austenitic stainless steels or non-ferrous metals. Converted values are approximations and do not replace a measurement. For tensile strength the standard quotes a scatter of about ±85 N/mm². Values between two table rows are linearly interpolated.
Hardness comparison table to ISO 18265
Table A.1 for unalloyed and low-alloy steels and cast steel, from 80 to 940 HV. Empty fields are left empty by the standard itself. HRB values in brackets lie outside the valid range of the scale and are not used by the converter.
| HRC | HB | HV | HRB | N/mm² |
|---|---|---|---|---|
| – | 76 | 80 | – | 255 |
| – | 80.7 | 85 | 41.0 | 270 |
| – | 85.5 | 90 | 48.0 | 285 |
| – | 90.2 | 95 | 52.0 | 305 |
| – | 95 | 100 | 56.2 | 320 |
| – | 99.8 | 105 | – | 335 |
| – | 105 | 110 | 62.3 | 350 |
| – | 109 | 115 | – | 370 |
| – | 114 | 120 | 66.7 | 385 |
| – | 119 | 125 | – | 400 |
| – | 124 | 130 | 71.2 | 415 |
| – | 128 | 135 | – | 430 |
| – | 133 | 140 | 75.0 | 450 |
| – | 138 | 145 | – | 465 |
| – | 143 | 150 | 78.7 | 480 |
| – | 147 | 155 | – | 495 |
| – | 152 | 160 | 81.7 | 510 |
| – | 156 | 165 | – | 530 |
| – | 162 | 170 | 85.0 | 545 |
| – | 166 | 175 | – | 560 |
| – | 171 | 180 | 87.1 | 575 |
| – | 176 | 185 | – | 595 |
| – | 181 | 190 | 89.5 | 610 |
| – | 185 | 195 | – | 625 |
| – | 190 | 200 | 91.5 | 640 |
| – | 195 | 205 | 92.5 | 660 |
| – | 199 | 210 | 93.5 | 675 |
| – | 204 | 215 | 94.0 | 690 |
| – | 209 | 220 | 95.0 | 705 |
| – | 214 | 225 | 96.0 | 720 |
| – | 219 | 230 | 96.7 | 740 |
| – | 223 | 235 | – | 755 |
| 20.3 | 228 | 240 | 98.1 | 770 |
| 21.3 | 233 | 245 | – | 785 |
| 22.2 | 238 | 250 | 99.5 | 800 |
| 23.1 | 242 | 255 | – | 820 |
| 24.0 | 247 | 260 | (101.0) | 835 |
| 24.8 | 252 | 265 | – | 850 |
| 25.6 | 257 | 270 | (102.0) | 865 |
| 26.4 | 261 | 275 | – | 880 |
| 27.1 | 266 | 280 | (104.0) | 900 |
| 27.8 | 271 | 285 | – | 915 |
| 28.5 | 276 | 290 | (105.0) | 930 |
| 29.2 | 280 | 295 | – | 950 |
| 29.8 | 285 | 300 | – | 965 |
| 31.0 | 295 | 310 | – | 995 |
| 32.2 | 304 | 320 | – | 1,030 |
| 33.3 | 314 | 330 | – | 1,060 |
| 34.4 | 323 | 340 | – | 1,095 |
| 35.5 | 333 | 350 | – | 1,125 |
| 36.6 | 342 | 360 | – | 1,155 |
| 37.7 | 352 | 370 | – | 1,190 |
| 38.8 | 361 | 380 | – | 1,220 |
| 39.8 | 371 | 390 | – | 1,255 |
| 40.8 | 380 | 400 | – | 1,290 |
| 41.8 | 390 | 410 | – | 1,320 |
| 42.7 | 399 | 420 | – | 1,350 |
| 43.6 | 409 | 430 | – | 1,385 |
| 44.5 | 418 | 440 | – | 1,420 |
| 45.3 | 428 | 450 | – | 1,455 |
| 46.1 | 437 | 460 | – | 1,485 |
| 46.9 | 447 | 470 | – | 1,520 |
| 47.7 | 456 | 480 | – | 1,555 |
| 48.4 | 466 | 490 | – | 1,595 |
| 49.1 | 475 | 500 | – | 1,630 |
| 49.8 | 485 | 510 | – | 1,665 |
| 50.5 | 494 | 520 | – | 1,700 |
| 51.1 | 504 | 530 | – | 1,740 |
| 51.7 | 513 | 540 | – | 1,775 |
| 52.3 | 523 | 550 | – | 1,810 |
| 53.0 | 532 | 560 | – | 1,845 |
| 53.6 | 542 | 570 | – | 1,880 |
| 54.1 | 551 | 580 | – | 1,920 |
| 54.7 | 561 | 590 | – | 1,955 |
| 55.2 | 570 | 600 | – | 1,995 |
| 55.7 | 580 | 610 | – | 2,030 |
| 56.3 | 589 | 620 | – | 2,070 |
| 56.8 | 599 | 630 | – | 2,105 |
| 57.3 | 608 | 640 | – | 2,145 |
| 57.8 | 618 | 650 | – | 2,180 |
| 58.3 | – | 660 | – | – |
| 58.8 | – | 670 | – | – |
| 59.2 | – | 680 | – | – |
| 59.7 | – | 690 | – | – |
| 60.1 | – | 700 | – | – |
| 61.0 | – | 720 | – | – |
| 61.8 | – | 740 | – | – |
| 62.5 | – | 760 | – | – |
| 63.3 | – | 780 | – | – |
| 64.0 | – | 800 | – | – |
| 64.7 | – | 820 | – | – |
| 65.3 | – | 840 | – | – |
| 65.9 | – | 860 | – | – |
| 66.4 | – | 880 | – | – |
| 67.0 | – | 900 | – | – |
| 67.5 | – | 920 | – | – |
| 68.0 | – | 940 | – | – |
Why hardness values can only be converted approximately
Each hardness test measures something different. Vickers presses a diamond pyramid into the surface and measures the diagonals, Brinell uses a ball and measures the diameter, Rockwell measures the permanent indentation depth. There is no fixed mathematical relationship between the scales.
The conversion table in ISO 18265 is therefore based on comparative measurements. It applies to the material it was determined on and is only an indication for anything else. The standard says so explicitly: a converted value is neither proof that a specification is met nor grounds for a complaint.
The least reliable value is tensile strength. The standard quotes a scatter of about ±85 N/mm², and for pearlitic steels between 300 and 500 HV the real value is on average about 100 N/mm² higher. If you really need the tensile strength, run a tensile test.
From the shop floor: If the drawing says 58 HRC, the part is tested in HRC, not measured in HV and converted. Conversion is meant for cases where the specified method cannot be used on the part, for example because it is too thin or too small for Rockwell. The standard then requires converting the mean of at least three individual readings, not a single value.
Frequently asked questions
How many HRC is 400 HV?
According to ISO 18265, 400 HV corresponds to about 40.8 HRC and 380 HB, with a tensile strength of about 1,290 N/mm². That is a row taken directly from the table, without interpolation.
How many HV is 60 HRC?
About 698 HV, interpolated between 690 HV (59.7 HRC) and 700 HV (60.1 HRC). There is no Brinell value for 60 HRC, because the table only lists Brinell up to 618 HB, which corresponds to 650 HV or 57.8 HRC.
What tensile strength does a steel with 300 HB have?
According to the table about 1,015 N/mm², which corresponds to roughly 31.7 HRC. For tensile strength, however, the standard quotes a scatter of about ±85 N/mm². A reliable figure requires a tensile test.
Does the table also apply to stainless steel?
No. Table A.1 applies to unalloyed and low-alloy steels and cast steel. Austenitic stainless steels such as 1.4301 (304) or 1.4404 (316L) are not covered, nor are aluminium or copper alloys. For these materials the converter gives wrong values.
Can converted hardness values be used for acceptance?
Not according to ISO 18265. Converted values are explicitly informative only and are neither proof that a specification is met nor grounds for a complaint. Testing uses the method specified on the drawing.
Why does Brinell stop at 618 HB?
With very hard materials the test ball itself deforms and the result becomes unreliable. ISO 6506 therefore limits the Brinell method to 650 HBW, and the conversion table ends at 618 HB. Hardened steels are tested in HRC or HV.
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