Rockwell Hardness Conversion Calculator

Rockwell hardness (HRC or HRB) measures the depth of indentation left by a diamond cone or steel ball under a fixed load. Brinell (HB) uses a larger ball indentor and measures the diameter of the indentation, making it better suited to rough or heterogeneous materials. Vickers (HV) uses a pyramid-shaped diamond indentor and applies across a wide range of materials and loads. All three measure resistance to plastic deformation but use different methods, so conversions between them are only approximate.

No — hardness conversions between scales are always approximate. Each scale uses a different indentor geometry, applied load, and measurement method, so a direct mathematical equivalence does not exist. The values produced by this calculator are based on standard reference tables (ISO 18265) and empirical data, and should be treated as guidelines rather than precise equivalents.

A Brinell hardness of 300 HB corresponds to approximately 315 HV (Vickers). This is an approximate value based on standard hardness conversion tables. The equivalent Rockwell C value is around 30 HRC, and the estimated tensile strength is roughly 1,000 N/mm².

Mild steel (low carbon steel) typically has a Brinell hardness of around 120–160 HB, which equates to roughly 120–170 HV and an HRB of approximately 68–85. It is generally too soft to be meaningfully measured on the Rockwell C (HRC) scale, which is better suited for harder steels.

For steel, there is a well-established empirical relationship between hardness and tensile strength. A common approximation is tensile strength (N/mm²) ≈ 3.3 × HB. This relationship is reasonably accurate for carbon and low-alloy steels but may not apply to stainless steels, cast irons, or non-ferrous metals.

Rockwell C (HRC) is used for harder materials, typically steel with HRC values between 20 and 70. Rockwell B (HRB) is better suited for softer materials such as non-hardened steel, aluminum, copper, and brass, covering the range of HRB 0–100. Using the wrong scale can result in inaccurate or invalid readings.

Strictly speaking, Brinell (HB), Rockwell (HRC/HRB), and Vickers (HV) hardness numbers are dimensionless — they do not carry traditional physical units like kg or N/mm². They represent relative scales derived from indentation test results rather than absolute physical quantities, which is why they cannot be directly compared without a conversion reference table.

Rockwell hardness (particularly HRC) is the most widely used scale in manufacturing and quality control due to its speed and ease of use — results are read directly from a dial without additional measurement steps. Brinell (HB) is common in raw material inspection and foundry work, while Vickers (HV) is favored in research and precision engineering because of its wide measurement range.