Hardness Conversion Calculator

Convert Rockwell HRC, HRB, Brinell HB, and Vickers HV hardness scales using ASTM E140 tables. Free converter for metallurgy, quality control, and testing.

Convert hardness scales

About This Calculator

This Hardness Conversion Calculator converts between the four most common material hardness scales: Rockwell C (HRC), Rockwell B (HRB), Brinell (HB), and Vickers (HV). Whether you are a metallurgist, quality control engineer, or materials scientist, accurate hardness conversion is essential for comparing material specifications across different standards and ensuring proper material selection for engineering applications.

The converter uses lookup tables based on ASTM E140 standard practice, which is the internationally recognized standard for hardness conversion of carbon steels, alloy steels, and tool steels. The conversion goes through Brinell (HB) as the intermediate reference scale. While conversions are never perfectly exact due to material-specific behaviors such as elastic modulus variations, work hardening characteristics, and alloy composition differences, these ASTM-based conversions provide the best available estimates suitable for most engineering applications.

Understanding Hardness Testing Methods

Hardness testing measures a material's resistance to plastic deformation by applying a controlled force with a specific indenter. Rockwell tests measure indentation depth using either a diamond cone (HRC) or a steel ball (HRB), making them quick and suitable for production quality control. Brinell tests use a carbide ball indenter and measure the diameter of the resulting indentation, making them ideal for castings and materials with non-uniform grain structures. Vickers tests use a diamond pyramid indenter and are suitable for thin materials, case-hardened layers, and precise laboratory measurements across the entire hardness range.

Hardness Scale Applications

  • HRC (Rockwell C): Hardened steels, tool steels, carbides (range: 20-70 HRC)
  • HRB (Rockwell B): Soft steels, brass, aluminum, plastics (range: 20-100 HRB)
  • HB (Brinell): Castings, forgings, large samples (range: 60-650 HB)
  • HV (Vickers): Thin materials, case-hardened layers, all metals (range: 100-950 HV)

Important Limitations

Hardness conversions are approximate estimates and should be treated as such. Different materials with identical hardness on one scale may show different values on another scale due to differences in elastic modulus, yield strength, and work hardening behavior. The ASTM E140 standard provides separate conversion tables for different material families including carbon steels, alloy steels, tool steels, nickel alloys, and non-ferrous metals. This calculator specifically implements the carbon and alloy steel conversion tables. For applications requiring precise hardness specification, always perform the actual hardness test on the appropriate scale rather than relying solely on converted values.

Frequently Asked Questions

What are the different hardness scales?

The four main hardness scales are: Rockwell C (HRC) for hard steels like tool steels, Rockwell B (HRB) for softer metals like brass and aluminum, Brinell (HB) for castings and larger samples, and Vickers (HV) for thin materials and precise measurements. Each uses different indenter types and test forces.

How is hardness conversion performed?

Hardness conversion follows ASTM E140 standards, which provide empirical formulas and lookup tables for converting between scales. The conversion typically goes through Brinell (HB) as the intermediate scale. For example, HRC is converted to HB, then HB is converted to the target scale using scale-specific formulas.

What is the difference between HRC and HRB?

HRC (Rockwell C) uses a diamond cone indenter with a 150 kg load and is used for hard materials like hardened steel and carbide. HRB (Rockwell B) uses a 1/16-inch steel ball indenter with a 100 kg load and is used for softer materials like annealed steel, brass, and aluminum alloys.

Which hardness scale should I use?

Choose HRC for hardened steels (20-70 HRC), HRB for soft metals (20-100 HRB), HB for large or rough samples (up to 650 HB), and HV for thin sections or case-hardened layers. Vickers is the most versatile because it uses a diamond indenter and works across the full hardness range.

Are hardness conversions exact?

No, hardness conversions are approximate and should be treated as estimates rather than exact equivalents. Different materials with the same hardness on one scale may differ on another scale due to variations in elastic modulus, work hardening, and material composition. ASTM E140 provides the best available standard conversions.

What is the relationship between HB and HV?

For most steels, Brinell (HB) and Vickers (HV) values are approximately equal, with HB slightly lower than HV. The approximate relationship is HV ≈ HB / 0.95. This close correlation exists because both tests use similar indentation principles, though Vickers uses a diamond pyramid instead of a carbide ball.

What is ASTM E140?

ASTM E140 is the standard practice for converting hardness readings between different scales and material types. It provides conversion tables and equations for Rockwell, Brinell, Vickers, and other hardness scales, covering carbon steels, alloy steels, tool steels, nickel alloys, and non-ferrous metals.

Can hardness conversion be done for non-ferrous metals?

Yes, but ASTM E140 provides separate conversion tables for different material families. Steel conversions do not apply directly to aluminum, copper, brass, or other non-ferrous metals. For accurate results, always use the material-specific conversion table that matches your alloy type.