Metal Hardness Chart: Rockwell vs Brinell vs Vickers Explained

Hardness measures how well a metal resists permanent deformation. That is, how it holds up when something harder presses into its surface. Rockwell, Brinell, and Vickers are all indentation tests, and they work the same basic way. You push an indenter into the material under a controlled load, then measure what it leaves behind. What separates Rockwell, Brinell, and Vickers is indenter shape, applied force, and how the result is read.

For engineers and QA teams reviewing certifications, a metal hardness chart is one of the most-referenced shop documents. It tells you whether a part was heat-treated correctly, whether incoming material meets spec, and—within limits—what tensile strength to expect. 

Comparing Rockwell, Brinell, and Vickers Side by Side

When selecting a test, there are some differences that are more important than others.

For full hardness conversion values across HRC, HRB, HB, and HV, use a metal hardness chart.

Rockwell Hardness (HRC, HRB, HRA)

So, what is Rockwell hardness? It’s a depth-based measurement. The shallower the indentation, the harder the material and the higher the number. Each scale carries a letter suffix pairing a specific indenter with a specific load.

How the Rockwell test works

A minor load seats the indenter to set a reference point. A major load follows, then releases, and the machine reads the depth of permanent penetration. The result can be read directly from the machine, with no optical measurement required. It’s a relatively fast test, and this speed makes Rockwell particularly useful for production testing. When running incoming inspection on tool steel bar or verifying heat treatment on stainless steel parts, you get a number fast enough to keep production moving.

Common Rockwell scales and when to use them

Rockwell has 30 standard scales (15 regular and 15 superficial), but in metalworking most testing uses just a few.

• HRC: diamond cone, 150 kgf. Hardened steels, tool steels, and heat-treated alloys above roughly 20 HRC.
• HRB: 1/16 in. ball, 100 kgf. Softer steels, brass, aluminum, and copper alloys.
• HRA: diamond cone, 60 kgf. Cemented carbides and thin case-hardened surfaces.
• HR15N, HR30N, HR45N: superficial scales, lower loads for thin specimens and coatings.

Deciding HRC vs HRB comes down to where your material sits. In the overlap around 20–25 HRC, test both and note which reads more reliably for your thickness.

Brinell Hardness (HB / HBW)

Brinell is more tolerant of rough or heterogeneous material than tests that rely on smaller indentations, which makes it useful for castings, forgings, and heavy stock.

How the Brinell test works

A 10 mm tungsten carbide ball presses in under heavy load and holds for 10–15 seconds. This is typically 3,000 kgf for steel, and 500 kgf for softer metals. The impression is measured optically, and HBW comes from the load divided by the curved area of the indent. Because the ball is large, each reading averages across a wide area, smoothing out porosity in castings and grain-size variation in forgings.

Where Brinell is the right choice

Brinell is standard for raw and semi-finished stock, like castings, forgings, large bar, and plate. It also suits annealed or normalized metals in the softer-to-mid range. Mill test reports for plate and bar routinely quote Brinell, so buyers and QA teams need the scale when reviewing certifications. The tradeoff is specimen size. Using a heavy load and wide indent rules out thin sections, finished surfaces, and small parts.

Vickers Hardness (HV)

Vickers is the most versatile of the three, but also the slowest. One continuous scale covers soft annealed aluminum through case-hardened steel, which is why failure analysis and research labs default to it.

How the Vickers test works

The Vickers hardness test pushes a 136° diamond pyramid into the surface under a controlled load. Both diagonals of the square impression are measured under a microscope, and HV comes from the load divided by the indent surface area. Because the same indenter geometry is used across a wide range of test forces, Vickers provides a single hardness scale without switching between scales such as HRC and HRB. At low test forces, however, measured hardness can still vary with indentation size.

Where Vickers fits best

Thin sections, coatings, case-depth evaluation, and very small parts where a Brinell or Rockwell indent would be too wide or too deep. In production, the Vickers hardness test checks case depth on carburized gears, coating hardness, weld heat-affected zones, and hardness gradients across a cross-section. Microhardness variants below 1 kgf can even measure individual phases in a microstructure. The cost, however, is prep time. There’s a polished or ground finish and optical measurement of every indent, which makes Vickers less practical than Rockwell for high-volume QC.

Which Hardness Test Should You Use?

Picking among hardness testing methods comes down to material type, geometry, surface condition, and throughput.

• Fast production QC on steel – choose Rockwell. You get direct readout, minimal operator judgment, seconds per test.
• Hardened or heat-treated steel – use HRC. It’s the standard scale for verifying quench-and-temper results.
• Softer steel or non-ferrous metals – HRB or Brinell, depending on surface condition and specimen size.
• Castings, forgings, rough surfaces, or coarse-grained metals – choose Brinell. The large ball averages out local inconsistencies.
• Thin sections, coatings, case depth, or very small parts – choose Vickers. The small indent won’t break through thin layers.
• Full range of materials on one continuous scale – use Vickers. There’s no scale switching required.

What You Need to Know About Hardness Conversion 

Engineers often need to compare values across metal hardness scales, like an HRC number on a mill cert against a Brinell spec on a drawing. Metal hardness conversion is possible, but approximate. The relationships are empirical, derived from comparison testing, not calculated. ASTM E140 provides material-specific conversion tables for several metal groups, including steels, nickel alloys, brass, copper, and wrought aluminum. Use the table that matches the material being tested rather than applying a steel conversion to another alloy family.

• Conversions are most accurate for steel in the mid-to-high hardness range.
• Below about 20 HRC, Rockwell C loses reliability. Use HRB or Brinell, then convert if needed.
• Non-ferrous alloys don’t follow steel’s conversion curves. Treat cross-scale numbers as rough estimates.
• ASTM E140 and ISO 18265 differ slightly in places, so metal hardness conversion results vary by source.

For the full lookup table across HRC, HRB, HBW, HV, and approximate tensile strength, use the Hardness Conversion Chart.

Hardness and Tensile Strength

For carbon and alloy steels, hardness correlates reasonably well with ultimate tensile strength, since both reflect resistance to plastic deformation. That’s why hardness testing works as fast verification of heat treatment. The rough conversion is to multiply the Brinell number by 500 for an estimate in psi, or by 3.45 for MPa. This is sometimes close enough for acceptance checks, but not a substitute for tensile testing.

The caveat is important. For non-ferrous alloys (aluminum, copper, titanium, nickel-based superalloys) the correlation is much weaker and varies by alloy family. Don’t apply steel-derived factors to them. If a spec calls for tensile data, test tensile.

Hardness sits alongside density and machinability when comparing candidate alloys.

Frequently Asked Questions

What is the difference between Rockwell, Brinell, and Vickers hardness?

Rockwell reads penetration depth directly, so it’s fast enough for production QC. Brinell uses a large ball and measures impression diameter, suiting castings, forgings, large bar, and coarse-grained stock. Vickers uses a diamond pyramid and measures the impression diagonals, suiting thin sections, coatings, and micro-scale work. Each reports on its own scale (HRC, HBW, HV), and values can be approximately converted using ASTM E140.

What does HRC mean?

HRC denotes Rockwell hardness measured on the C scale: a diamond cone indenter, 150 kgf major load. It’s the standard for hardened and heat-treated steels, typically covering 20–70 HRC.

What is the difference between HRC and HRB?

HRC uses a diamond cone at 150 kgf for hardened metals, roughly 20–70 HRC. HRB uses a 1/16 in. tungsten carbide ball at 100 kgf for softer metals (annealed steels, brass, copper, aluminum) up to about 100 HRB. In the overlap zone, HRC vs HRB comes down to condition: HRC for heat-treated steel, HRB for unhardened stock.

Which hardness test is most accurate?

There isn’t one hardness test that is most accurate in every application. Vickers is well suited to thin sections, coatings, case-depth measurements, and small parts because it uses a small diamond indentation and works across a wide hardness range. Rockwell is usually the better choice for fast, repeatable production testing because the result is read directly from penetration depth with minimal operator interpretation. Brinell is often more representative for castings, forgings, and coarse or uneven materials because its larger indentation averages hardness over a wider area. All three depend on calibration, surface prep, specimen thickness, and the governing ASTM standard.

Can you convert Brinell to Rockwell?

Yes, approximately, using ASTM E140 or ISO 18265. The conversions are empirical, based on comparison testing rather than calculation, and ASTM E140 provides separate tables for steels, nickel alloys, brass, copper, and wrought aluminum. Always use the table for your material family. Conversions are most reliable for carbon and alloy steels within their stated ranges and less reliable for other alloys. A metal hardness chart can help with the conversions.

What is the hardest metal on the hardness scale?

Among pure metals, chromium is usually ranked hardest, at about 8.5 on the Mohs scale, with tungsten and osmium close behind. In practice, the hardest materials used in metalworking aren’t pure metals. Cemented tungsten carbide (tungsten carbide bonded with cobalt), used for cutting tools and wear parts, typically measures about 1,300–2,000 HV depending on grade. Hardened tool steels typically reach 58–65 HRC, roughly 650–830 HV.

How is hardness related to tensile strength?

For carbon and alloy steels they correlate reasonably well, since both reflect resistance to plastic deformation. As a rough estimate, multiply the Brinell number by 500 for psi (or by 3.45 for MPa). The rule works best for steels below about 500 HB. The relationship is specific to steel. For aluminum, copper, titanium, and nickel alloys it’s weaker and alloy-dependent, so don’t rely on it.

Need hardness values for a specific alloy or grade? Use Tech Steel’s Hardness Conversion Chart for the full lookup table, or request a quote for material to spec.

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