Metal Hardness Scale: 4 Main Types Explained (2026 Guide)

A metal hardness scale is a ranking of the resistance of a metal to permanent indentation. The leading scales are Rockwell (HRB, HRC), Brinell (HB), Vickers (HV), and the Mohs scratch scale. Each employs an alternative scoring system and testing system, and values can only be roughly converted and thus should be compared on the same metric.

You've probably come across a spec saying 58–62 HRC or a chart showing the same metal with three hardness values. Most charts do not indicate which scale and condition a number comes from, or when it can be safely converted. This 2026 guide helps you understand how each scale works, where common metals fall, and how to compare the numbers without getting misled.

Key Takeaways

● Metal hardness scales assess the ability of a specimen to resist a permanent indentation or scratching.‌ No single metal hardness scale is suitable to cover all metals.

● Rockwell, Brinell and Vickers belong to three indentation scales that are primarily used for metals and differ by the indenter, load and what is measured.

● The softer metallic materials like copper alloys and aluminum are machined by the Rockwell B while the harder steels are machined by the Rockwell C. I can't send you my answer.

● The Mohs scale classifies scratch resistance, ranging from 1 (for talc) to 10 (for diamond); this scale is too coarse for engineering metals.

● The conversion charts between scales given in this specification are approximate. The ASTM E140 tables apply only to specific materials.

● Which scale you choose is dependent on the part and material. For fast production checks use Rockwell, Brinell for castings and forgings, Vickers for thin sections, coatings and microhardness.

● Correctly reading any hardness number requires knowing the scale, the load, and the material condition, so record all three.

What Is a Metal Hardness Scale, and Why Is There More Than One?

A metal hardness scale is a standard measurement that rates a metal’s resistance to permanent indentation (measured, for example, by Rockwell, Brinell, and Vickers) or scratching (such as measured by Mohs). Different scales provide alternative references depending on the questions being posed.

The scales can be grouped into three families.

● Mohs scale ranks which materials can scratch which.

● The depth or size of a dent created by Rockwell, Brinell, and Vickers test gives the indentation hardness of a material. The Rockwell test measures by depth while others rely on size.

● The Leeb test drops a small impact body and measures how fast it bounces back; it is reported as HLD.

This is the pragmatic consequence. A depth reading, a dent-width reading and a bounce reading are all measurements. A number from one family represents a translation of another, never the same number. This is why a datasheet specifying 95 HB and another showing 60 HRB can refer to the same aluminum.

There are a couple of indentation techniques found in niche work. The Knoop test employs an elongated diamond for very thin or brittle samples. The leeb test is useful for large pieces which can not be transported to a lab.

Can You Use the Mohs Scale to Measure Metal Hardness?

It is possible, but the outcome is too unrefined for any engineering application. The 1812 Mohs scale was invented by Friedrich Mohs and ranges from 1 (talc) to 10 (diamond). According to the Metals4u blog, industrial metals are seen as too inaccurate.

The evaluation is uncomplicated. If material A scratches material B, then A is harder. Pure gold sits at around 2.5, steel can be as high as 8 (Metals4u, 2026).

This means that Mohs only provides rank order. It cannot indicate one material’s degree of hardness versus that of another.

The distribution shows how widespread this is. According to Metal Supermarkets (Source: Metal Supermarkets, c. 2022) the hardness of steel is rated at 4, which is 5 rated according to Rivcut (Rivcut, 2026), while The Metal Store (Source: The Metal Store, undated) lists it as 4 to 8. A four to eight spread for one metal family covers four of the nine steps between one and ten, or about 44 percent of the scale.

It is hard to put ductility and work hardening metals on Mohr’s Scale of Minerals. When referring to various metals, follow Mohs hardness values closely for pure metals, but not for alloys and treated metals.

How Do Rockwell, Brinell, and Vickers Work?

The three primary indentation tests for metals are Rockwell, Brinell, and Vickers, and each one is specified according to its indenter and load. The main standards are ASTM E18 (Rockwell), E10 (Brinell), E92 (Vickers macro), E384 (Vickers and Knoop micro), and E140 (conversion tables) (Infinita Lab, 2026).

Rockwell (HRB, HRC)

The Rockwell test examines how deeply an indenter penetrates under load. The scale B uses a 1/16-inch steel ball at 100 kg to test softer materials. These include copper alloys, soft steel, and aluminum alloys. The C scale utilizes a diamond cone with a 120° angle and 150 kg for harder materials (University of Maryland CALCE). HRC usually lies between 20 and 70. ISO 6508 is the international standard for hardness.

Brinell (HB, HBW)

The Brinell test uses a hard ball to press the metal and the width of the dent is measured. Its large impression averages over a coarse grain, so it works well with castings and forgings. This method is unsuitable for very hard materials or smaller components (Xometry,2025). ISO 6506 includes it.

Vickers (HV)

According to Infinita Lab (2026), the Vickers hardness test employs a square-based diamond pyramid subjected to loads ranging from 10 gf to 50 kgf. You observe the dent's diagonals under a microscope. It’s accurate. However, this requires optical systems and sample preparation which makes it more costly and takes longer to run than Rockwell (Source: ESICT ET 2023). The ISO 6507 standard applies.

Notation Decoder

Properly interpreting the label is as important as the figure.

● 58 HRC indicates when measuring steel on the Rockwell scale that it is hardened steel.

● The hardness of the material is 60 on the Rockwell B scale.

● This refers to Brinell hardness testing performed with a tungsten carbide ball, 10 mm wide under a 3000 kgf load.

● The Vickers hardness subject to a load of 5 kgf.

Without letters a number is incomplete. You cannot compare it to anything without the scale and load.

Which Hardness Scale Should You Use?

The suitable scale depends upon the material, size and surface of the part, and how fast you need results. Comparison of the four Scales is done through this table.

Apply this decision flow depending on part condition.

1. Hardened steel, high volume: Rockwell C (ASTM E18).

2. One can use either Rockwell B, or Brinell for thicker stock, but the softer metals are ones like aluminum or copper alloys.

3. Brinell test for coarse-grained casting or forging.

4. Vickers (ASTM E92 or E384) are used for thin, coated, or very small features.

5. A portable Leeb rebound tester is a large, installed component that cannot be moved.

Apattern emerges in this flow; the choice depends rarely on the name of the metal. The size of the dent can depend on the size of the part. If a dent exceeds the dimension of a thin sheet or coating, it will not yield a genuine reading. So, the size rules hardness in this case.

Metal Hardness Chart by Alloy and Condition

A hardness chart sets forth for every value its scale and material condition. The values used in this table are all valued according to a scale or a source.

Please note the repeated appearance of ‘6061-T6’ which was chosen to represent aluminum on the scales. Just as much as Form, Condition matters: T6 is a temper and the same alloy in another temper gives different numbers. Steel has similar properties. Out of the five pages of competitors that we reviewed for this guide, only Rivcut shows grade and temper together.

Where Charts Disagree

According to Proleantech (2026),6061-T6 exhibits HRB 60 according to ASTM, 40 according to GM Spec which matches Rivcut. The untracked HRC-style figure is the problem. According to Rivcut no HRC value is given for 6061-T6, TechSteel indicates HRC refers to steels over approximately 20 HRC. Proleantech rates lead as HRB 5, and its values for 304 stainless differ from Rivcut's. When confronted with two opposing charts, trust the one that names the scale and condition, then refer to the mill cert.

How Do You Convert Rockwell to Brinell or Vickers, and How Accurate Is It?

According to ASTM E140, the hardness conversions between Rockwell, Brinell and Vickers aren’t “exact” but “approximate” and they have tables for each material . According to the standard "conversion is done with discretions and under controlled conditions" (ASTM International, 2019). LECO, a manufacturer of testing equipment states, “we can state it bluntly; it is impossible to make a proper conversion calculation using ASTM E140”.

A Case Where Conversion Fails

According to ASTM E140 Table 1, 286 Brinell equals 30 HRC. Private testing shows it converts to < 28 HRC in at least one duplex stainless steel (Valve Magazine, 2026). The stated 30 HRC contains a gap of more than 2 HRC points, which represents over 6%. On a spec with a narrow window, that error might permit a part that ought to fail.

The table scope is the reason E140 tables describe particular groupings, such as non-austenitic steels and austenitic stainless sheet copper. Employing a steel table on another alloy family introduces errors (Valve Magazine, 2026).

A Rule of Thumb and Tools

Only Convert Within The Same Family Of Material. For any drawing involving a scale, test the scale. The tables within ASTM E140 are the standard. Another alternative is the ZwickRoell hardness converter app, which allows conversions to the ISO 18265 and ASTM E140 scales and to tensile strength.

What Does a Hardness Number Not Tell You?

The hardness number of a material does not measure strength, toughness, or wear life. It indicates a surface's resistance to a small, local dent.

More hardness can also mean more brittleness. As per SA materials, a metal may bend before it breaks, a ceramic would break suddenly. Estimates, not test results, tensile-strength columns in conversion tables. When strength is an issue and you truly need to know it, then do a tensile test instead of just looking up the hardness chart.

Here is a practical solution to implement this. Consider using hardness as a screening check confirming the heat treatment is in the right range. If the part reads 58–62 HRC, it underwent a hardening step. However, this does not indicate that the part will not chip under impact.

Frequently Asked Questions

Which Hardness Test Is Best for Aluminum?

Rockwell B is the common selection for aluminum as its 100 kg load and steel ball are suited to soft metals. Brinell method is utilized for thicker stock. Do not use HRC, which is geared towards hard steels. For example, 6061-T6 reads about 60 HRB and 95 HB.

When Should You Use Vickers Microhardness Testing?

The Vickers microhardness test is ideal for thin sections, small parts, coatings, and tiny weld zones. Its minimum loads (10 gf) create a minimal dent. (Infinita Lab, 2026) ASTM E384 discusses microhardness. Prepare for a longer and costlier process than Rockwell.

Which Hardness Test Is Cheapest and Fastest for Production?

Rockwell is number one for the speed and cost of production. Because it reads depth directly, no microscope is needed. This is suitable to inspect numerous hardened steel components in every shift. Vickers' optical measurement and preparation takes longer and is more expensive. (Source: ESICT, about 2023)

How Does Heat Treatment or Temper Change a Metal's Hardness Number?

Heat treatment changes a metal's internal structure. The same alloy can read very differently before and after. Hardening increases the number but annealing decreases it. Aluminum tempers, for example T6, work in the same way. It is always helpful to keep the condition next to the number like 4140 annealed and 4140 hardened.

What Does HRC Mean in Metal Hardness?

HRC is a name for Rockwell hardness on the C scale. It uses a diamond cone and a 150 kgf major load, typically measuring 20 to 70 (TechSteel 2026) A reading of 58 HRC suggests the steel is very hardened like D2 tool steel, which lies in the range of of 58 HRC to 64 HRC.

Conclusion

Select the test most suitable to the material, component geometry, and what your spec calls for since the four scales complement each other. Before copying a hardness number to any drawing or purchase order, check the scale, the load and the material condition on the report. When a specification requires a value in a different scale, always ask for a test in that scale, not a conversion chart.