Hardness Conversion Calculator

These rows come from Table 1 of ASTM E140-07 (carbon, alloy and tool steels). The current edition is E140-12b(2019)e1, so compare against it before you use a value for acceptance.

Brinell numbers in brackets are outside the range the Brinell test method recommends, so treat them as extrapolations.

For softer steel, the Rockwell B range is in Table 2. In this range Vickers and Brinell have the same number:

Readings between rows are interpolated in a straight line. For HRC 47.5, HV lies between 471 and 484, giving about 478.

A Brinell reading of 300 lies between 294 (HRC 31) and 301 (HRC 32), which gives 31.9, reported as HRC 32. The standard rounds converted Rockwell numbers to whole numbers because the conversion is not precise enough for decimals.

Tables 1 and 2 are for non-austenitic steels, including carbon, alloy and tool steels, in the forged, annealed, normalized, or quenched and tempered condition, as long as they are uniform through the section.

Other materials have their own tables in E140. Applying the steel table to them gives wrong numbers.

Case-hardened parts are a separate trap. A surface reading of HRC 60 says nothing about the core, and a heavy Brinell or Vickers load may reach through a thin case. Thin parts need a lighter load, and the guide to heat treatment explains how the case forms.

ASTM E140 itself says conversion should be used only when the material cannot be tested under the specified conditions. If a drawing calls for 38–42 HRC, test on Rockwell C. A converted value should not settle an acceptance dispute, because a real test outranks a table.

State the scale fully on a drawing, for example "HV 10" and not just "HV", and name the test standard. The hardness entry in the glossary compares how each test works.

For plain carbon and low-alloy steels, a rule of thumb links Brinell hardness to tensile strength:

• UTS in psi ≈ 500 × HB
• UTS in MPa ≈ 3.45 × HB

So 300 HB suggests about 150 ksi, or 1,035 MPa. This is an estimate, not a test result. It is not part of ASTM E140, and it does not hold for stainless steels, aluminium or other non-ferrous metals. Ductility cannot be read from hardness at all, and a harder steel may also be much harder to weld. The yield strength calculator covers the next step, and the steel heat treatment table links hardness to tempering.

The scleroscope is a rebound test for metals. Shore A and Shore D are durometer scales for rubber and plastics. Both have "Shore" in their history, and they have nothing to do with each other. Do not read one as the other.