Metal Hardness Conversion Calculator
Enter hardness in any scale and get all equivalents: Rockwell HRC, Rockwell HRB, Vickers HV, Brinell HB, and approximate tensile strength. ASTM E140 based. Nothing uploaded.
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Equivalents
Learn more: metal hardness scales and conversions
Why multiple hardness scales exist and what they measure
Different hardness scales were developed for different materials and applications. Rockwell C (HRC) is best for hard steels. Rockwell B (HRB) is for softer materials. Vickers (HV) and Brinell (HB) scales measure hardness by indenting the material and measuring the indent size. The different indenter shapes and loads make direct numerical comparison impossible - a 60 HRC steel is not "twice as hard" as a 30 HRC steel. This is why conversion tables (ASTM E140) use empirical data to map equivalencies.
HRC and HRB - scale selection and measurement range
HRC (Rockwell C scale) uses a diamond cone indenter and a 150kg load. It is sensitive to hard steels (typically 20-68 HRC). Below 20 HRC, the indenter penetrates too deep and readings become unreliable - use HRB instead. HRB uses a 1/16 inch ball indenter and 100kg load, and measures softer materials like aluminium, copper, brass, and low-carbon steel. The two scales are not comparable - a reading must stay on the same scale or be converted using a reference table.
Tensile strength estimates from hardness - empirical correlations
For carbon and low-alloy steels, hardness has a rough correlation with tensile strength (UTS). A common approximation is UTS (MPa) ≈ 3.4 × HV for Vickers or 0.36 × HB for Brinell. This is accurate to about ±10-15% and works well for heat-treated steels in the typical hardness range. It does NOT apply reliably to aluminium, cast iron, copper, or highly alloyed materials. Hardness alone cannot predict UTS for all materials - it is a useful rule of thumb for steels only.
FAQ
What hardness scale should I use?
It depends on the material and expected hardness range. Hard steels: HRC. Softer steels, aluminium, copper: HRB. When in doubt, HV (Vickers) is universal and works across all hardness levels. Brinell (HB) is traditional in foundry and materials labs.
How accurate are these conversions?
ASTM E140 conversions are empirical and typically accurate to ±2-5 points on the hard-to-soft scale (e.g., HRC to HB). The conversion is non-linear and works best within the middle of each scale's range. Extreme values have more uncertainty.
Can I use Vickers or Brinell to measure anything harder than HRC 68?
Yes. HRC saturates around 68. For extremely hard materials like carbide or ceramic, use HV (Vickers), which can measure up to about 2000 HV without issue.