Hardness Conversion Chart: HRC, HB and HV (With What Marks Each Hardness)

Type any reading into the calculator, or find your row in the hardness conversion chart below. Values follow ASTM E140 for non-austenitic steels and are approximate.

A hardness number is only half the answer. The other half is what you can still do to the part. At HeatSign, the question behind most hardness lookups is simple: will this part take a permanent mark (a serial number, heat number or Data Matrix code, a small square barcode), and with which tool? This page gives you both.

What is the hardness conversion chart for hardened steel (HRC 20–68)?

For hardened carbon, alloy and tool steels, use this Rockwell C steel hardness chart. 60 HRC ≈ 697 HV ≈ 654 HB, 50 HRC ≈ 513 HV ≈ 481 HB, and 40 HRC ≈ 392 HV ≈ 371 HB. Values follow ASTM E140 Table 1 and are approximate.

Brinell (HB) uses a 10 mm ball at 3,000 kgf. Above 450 HB the ball is tungsten carbide, and above 65 HRC there is no Brinell value. Tensile strength is an estimate for carbon and alloy steels only; MPa is converted from ksi.

What about softer metals on the Rockwell B scale?

Below about 20 HRC, switch to the Rockwell B hardness chart. For non-austenitic steels, 100 HRB ≈ 240 HV ≈ 800 MPa (116 ksi) tensile, 90 HRB ≈ 185 HV and 80 HRB ≈ 150 HV. Above 100 HRB, the B scale loses accuracy, so test on the C scale instead.

In this range, Vickers and Brinell at 3,000 kgf read about the same, so they share a column. Brinell at 500 kgf is the load used for softer metals. The two charts meet at about 100 HRB, roughly 22 HRC.

How hard are common metals?

This metal hardness chart gives typical values. 6061-T6 aluminum is about 95 HB, A36 structural steel about 120–160 HB, and annealed 304 stainless at most 201 HB. Grade 8 bolts run 33–39 HRC, AR500 plate about 470–540 HB, and hardened D2 tool steel 58–62 HRC.

A36 does not set a hardness limit; the range is typical supplier data. Wear-plate hardness moves from mill to mill, so check the mill certificate.

Which marking method still works at each hardness?

Standard hand stamps are rated to about 28–35 HRC and hard-metal stamps to about 50 HRC. HeatSign dot peen markers mark parts up to 60 HRC. Above that, on hardened tool steel, carburized cases or carbide, use a fiber laser marking machine.

The stamp limits come from the catalog ratings we checked. General-purpose steel stamps list 28, 30 or 35 HRC as the maximum surface hardness. Stamps sold for stainless and heat-treated steel list 50 HRC. One knife maker put the wall a little higher: he knew of no stamp that works on heat-treated steel above about 54 HRC.

A dot peen marker has more room because its stylus (the pointed pin that strikes the part) is carbide. The HeatSign stylus is about 67 HRC, so it stays harder than the part up to 60 HRC. Near that limit the dots get shallower, so mark a sample first.

Marking parts above 50 HRC? See our fiber laser marking machines. Up to 60 HRC, dot peen marking machines cut a deeper mark for less money. For the full trade-off, read laser vs dot peen marking.

When is a hardness conversion not valid?

Conversions are estimates. ASTM E140 Tables 1–2 cover non-austenitic steels only; austenitic stainless, aluminum, brass and copper have separate tables. Avoid HRC below 20 and HRB above 100, and use tensile estimates only for carbon and alloy steels.

• It is an estimate. ASTM E140 calls conversion “only an approximate process” and advises against it whenever you can test on the scale you need.
• Match the table to the metal. The steel tables do not fit 304 or 316 stainless, aluminum, brass or copper. E140 has separate tables for cartridge brass (Table 4), austenitic stainless plate and sheet (Tables 5 and 6), copper (Table 7) and wrought aluminum (Table 9).
• Stay on the right scale. Readings below 20 HRC or above 100 HRB are not reliable. Retest on the other scale instead of converting.
• Carbide is tested on Rockwell A. The carbide test method (ASTM B294) uses HRA, so carbide never shows up in an HRC chart.

Which is harder, Rockwell B or C? For the same number, C is far harder: 20 HRC is about 98 HRB.

Not sure your part will take a mark?

The most common mistake we see is marking after heat treatment without checking the hardness first. A part that took a crisp stamp at 25 HRC can refuse the same stamp at 55 HRC.

If you are close to a limit, send HeatSign a sample piece and its hardness reading. We mark it with the method that fits and email you photos.