Guide
How do you read a hardness conversion chart for HRC, HV and HB, and when is it valid?
A hardness conversion chart is a table of approximate equivalent readings between hardness scales, such as Rockwell C, Vickers and Brinell, and the standard chart for steel is Table 1 of ASTM E140. It is valid only for the material family the table was built for, homogeneous non-austenitic steel in the case of Table 1, and a converted number is an estimate, so the drawing should name the scale that will actually be tested.
By Saola Manufacturing engineering team · Published · Updated
This guide is for engineers and quality staff who have a hardness requirement in one scale and a test result, a supplier report or a material certificate in another. The chart values below are taken from Struers’ hardness conversion table for non-austenitic steels, which the hardness-tester maker states follows ASTM E140 for the Rockwell C range; the scope and limits come from the published scope of ASTM E140 itself. Which scale to choose in the first place is covered in our Rockwell vs Brinell vs Vickers guide; this page is about reading across scales once a number exists.
On this page
What does the HRC to HV and HB chart say for steel?
Per ASTM E140 Table 1, 60 HRC on homogeneous steel corresponds to about 697 HV, 50 HRC to about 513 HV and 481 HBW, and 30 HRC to about 302 HV and 286 HBW.
The chart is read across a row: find the measured value in its column and read the estimated value in the other. Per ASTM E140 Table 1, the Brinell column assumes a 10 mm tungsten carbide ball at 3000 kgf, which is why the Brinell values from about 59 HRC upward appear in parentheses in the Struers chart; those are outside the range normally used for that test. The Brinell test itself is defined in ASTM E10 and the Rockwell tests in ASTM E18.
Interpolating between rows is acceptable for an estimate, but per the scope of ASTM E140 the values were obtained largely from computer-generated curves of test data, so reading more significant figures than the table prints adds no accuracy.
| Rockwell C (HRC) | Vickers (HV) | Brinell, 10 mm carbide ball, 3000 kgf (HBW) | Rockwell A (HRA) | Superficial 30N (HR30N) |
|---|---|---|---|---|
| 65 | 832 | (739) | 83.9 | 81.9 |
| 60 | 697 | (654) | 81.2 | 77.5 |
| 55 | 595 | 560 | 78.5 | 73.0 |
| 50 | 513 | 481 | 75.9 | 68.5 |
| 45 | 446 | 421 | 73.1 | 64.0 |
| 40 | 392 | 371 | 70.4 | 59.5 |
| 35 | 345 | 327 | 67.9 | 55.0 |
| 30 | 302 | 286 | 65.3 | 50.4 |
| 25 | 266 | 253 | 62.8 | 45.9 |
| 20 | 238 | 226 | 60.5 | 41.5 |
Which materials does the ASTM E140 chart apply to?
Only the material families named in its scope: separate tables cover non-austenitic steels, nickel alloys, cartridge brass, austenitic stainless steel, copper, alloyed white iron and wrought aluminum, and a table built for one family must not be used for another.
This is the limit most often missed. The familiar HRC-HV-HB chart is Table 1, and per the E140 scope it applies to carbon, alloy and tool steels in the as-forged, annealed, normalized and quenched and tempered conditions, provided that they are homogeneous. Using it for a stainless, a brass other than cartridge brass, a zinc die casting or a titanium part gives a number with no standing.
| Material on the drawing | E140 table | Limits stated in the scope |
|---|---|---|
| Carbon, alloy and tool steel, hardened range | Table 1 (Rockwell C range) | Non-austenitic, homogeneous; as-forged, annealed, normalized or quenched and tempered |
| Carbon and alloy steel, soft range | Table 2 (Rockwell B range) | Same conditions as Table 1 |
| Nickel and high-nickel alloys | Table 3 | Nickel content over 50 percent |
| Cartridge brass | Table 4 | Cartridge brass only, not every brass |
| Austenitic stainless steel | Tables 5 and 6 | Annealed plate (Brinell to Rockwell B) and sheet (Rockwell to superficial) |
| Copper | Table 7 | Copper |
| Wrought aluminum | Table 9 | Wrought products, not castings |
| Titanium, die-cast zinc, cast aluminum | None listed | Test in the specified scale; do not convert |
How accurate is a converted hardness value?
Treat it as an approximation with no stated confidence limit: ASTM E140 says conversion should be used only when the material cannot be tested under the conditions specified, and then with discretion and under controlled conditions.
The scope also warns that differences in sensitivity within one scale can be larger than the difference between two scales. A converted value therefore cannot settle a borderline result. If a typical requirement of 58-62 HRC applies and the report shows a Vickers reading that converts to just under the low limit, the right answer is a Rockwell C test, not a debate over the chart.
Rounding matters too. Per the E140 scope, most Rockwell numbers in the tables are given to the nearest 0.1 or 0.5, so a chart that prints a whole number and one that prints a decimal for the same row are equally approximate.
When should you not convert hardness at all?
Do not convert on case-hardened, plated, decarburized or very thin parts, because the scales press to different depths and the material is no longer homogeneous through the depth each test samples.
A Rockwell C indent and a light Vickers indent on a carburized surface sample different layers, so their readings disagree for a real physical reason, not a chart error. The same applies to induction-hardened shafts, nitrided parts and anything with a hard coating. For those, the drawing should name a surface test at a stated load or a microhardness traverse per ASTM E384 at a stated depth.
Cold-worked austenitic stainless is another trap. Per the E140 scope, the austenitic tables cover annealed plate and sheet; a cold-drawn 304 bar is outside them.
How should the drawing call out hardness so no conversion is needed?
Write the range in the scale that will be tested, with the test standard and, for Brinell or Vickers, the load: for example “HARDNESS 28-34 HRC PER ASTM E18” or “HARDNESS 241-285 HBW 10/3000 PER ASTM E10”.
Name where to test, too. A note such as “TEST ON END FACE, AFTER HEAT TREAT, BEFORE PLATING” removes most disputes, because it fixes the surface condition and the location before anyone argues about scales. If a mill certificate will report Brinell while your incoming inspection uses Rockwell, say on the drawing or PO which result governs.
For the bar and section sizes where a full-load test is impossible, allow a second scale explicitly, for example “HR30N PERMITTED ON SECTIONS TOO THIN FOR HRC; ACCEPTANCE BY CONVERSION PER ASTM E140 TABLE 1”. Then a conversion is a stated rule, not a judgment call at receiving.
How is a converted value reported, and how does Saola handle hardness on an order?
A converted value should always be labeled as converted, with the measured scale and the E140 table used; on our orders the measured scale is agreed at drawing review and stated on the inspection record.
A good report line reads “measured 68.5 HR30N, converted to about 50 HRC per ASTM E140 Table 1”, never a bare “50 HRC”. The lead plant’s inspection equipment includes a hardness tester, alongside a vision measuring instrument and a height gauge, and the scale and load available for a given part are confirmed when the drawing is reviewed. New parts get a first-article inspection report and every lot gets a dimensional inspection record; material certificates are available on request.
For machined steel parts on the CNC turning page, such as 52100 or 12L14 bar parts, send the hardness note exactly as written, including any heat-treat specification, so the review can confirm where and how it will be checked.
Frequently asked
Is HRC 50 the same as 500 HV?
No. Per ASTM E140 Table 1, 50 HRC on homogeneous steel converts to about 513 HV and 481 HBW. Close, but a spec written in one scale should be checked in that scale.
Can I convert Rockwell B readings on aluminum with the steel chart?
No. ASTM E140 has a separate Table 9 for wrought aluminum products. Use that table, or better, specify and test the aluminum in the scale the material specification names.
What do the values in parentheses on a hardness chart mean?
They mark readings outside the range where that scale is normally used, such as high Brinell values on hardened steel. Treat them as reference only, and test in a scale suited to that range.
Can hardness be converted to tensile strength?
Some charts add an approximate tensile column for steel, but ASTM E140 does not include one. For acceptance, use a tensile test or the material certificate, not a hardness conversion.
Is Leeb hardness covered?
Yes, for non-austenitic steels only. Per its scope, ASTM E140 Table 10 relates Leeb Type D readings to Brinell, Vickers and Rockwell for those steels.
Sources
- ASTM E140-12b(2019)e1, Standard Hardness Conversion Tables for Metals (scope), ASTM International, 2019
- Hardness Conversion Table for Non-Austenitic Steels (according to ASTM E140, Rockwell C range), poster 62142105, Struers, 2017
- ASTM E18-25, Standard Test Methods for Rockwell Hardness of Metallic Materials, ASTM International, 2025
- ASTM E10-23, Standard Test Method for Brinell Hardness of Metallic Materials, ASTM International, 2023
- ASTM E384-22, Standard Test Method for Microindentation Hardness of Materials, ASTM International, 2022