How We Calculated This
This converter uses the ASTM E140 standard conversion tables. These tables were built from thousands of empirical hardness tests on carbon and alloy steels. The conversions are interpolated between official data points to give smooth results at any input value.
Rockwell C (HRC)
HRC is the most common scale for heat-treated steel and tool steel. It uses a 150 kg load with a diamond cone indenter. The valid range is HRC 20 to 68. Below HRC 20, use the Rockwell B scale instead.
Rockwell B (HRB)
HRB is used for softer materials like annealed steel, brass 360, copper C110, and aluminum alloys. It uses a 100 kg load with a 1/16-inch steel ball indenter. The valid range is HRB 0 to 100.
Brinell (HB)
Brinell hardness uses a 10mm tungsten carbide ball with 3000 kg load. It works well for castings and forgings because the large indentation averages out surface irregularities. Common in steel specifications.
Quick rule of thumb: For carbon and alloy steels, tensile strength in ksi is roughly half the Brinell number. So 300 HB means about 150 ksi tensile strength.
Vickers (HV) and Knoop (HK)
Vickers uses a diamond pyramid indenter and works across the full hardness range. Knoop uses an elongated diamond and is best for thin materials and coatings. Both are common in metallurgical labs and on engineering drawings.
Tensile Strength Estimate
The tensile strength approximation is valid only for carbon and alloy steels. It does not apply to aluminum, stainless steel, brass, titanium, or other alloys. For those materials, consult the specific material data sheet.