Metal hardness gets measured on three different scales depending on the testing method used, this calculator converts between them, with the caveat that these conversions are empirical approximations, not exact physical equivalences.
How to use this hardness conversion calculator
- Enter a value and select your From unit (Brinell, Rockwell C, or Vickers).
- Select your To unit.
- Read the converted result instantly, or tap Swap Units to reverse the direction.
What this calculator does
Brinell (HB), Rockwell C (HRC), and Vickers (HV) are the three most common hardness scales for metals, each measured with a different indenter and load. For example, 250 HV is approximately 238.1 HB and approximately 35.5 HRC.
Example: 250 HV ≈ 238.1 HB ≈ 35.5 HRC
An important accuracy caveat
Hardness scale conversions are empirical approximations valid only within limited ranges (see ASTM E140 for authoritative tables), results outside typical metal-hardness ranges (roughly HV 200-940) may be inaccurate or undefined. Always use official ASTM E140 conversion tables for critical or engineering applications rather than relying on this calculator’s approximation for specification or quality-control decisions.
Why the three scales don’t convert with a fixed formula
Unlike a straightforward unit conversion (like inches to centimeters), each hardness scale measures a physically different response, indentation depth for Rockwell, indentation diagonal size for Vickers, indentation impression diameter for Brinell, using different indenters and applied loads. Because the underlying physical relationship between these measurements isn’t perfectly linear across the full hardness range, conversions are based on empirical correlation tables rather than a fixed mathematical formula.
Frequently asked questions
Are hardness conversions between scales exact?
No, they’re empirical approximations valid only within limited ranges, per ASTM E140. Results outside the typical metal-hardness range (roughly HV 200-940) may be inaccurate, always use official ASTM E140 tables for critical engineering applications.
Why can’t hardness scales be converted with a simple formula?
Each scale measures a physically different response (indentation depth, diagonal size, or impression diameter) using different indenters and loads, and the relationship between them isn’t perfectly linear, so conversions rely on empirical correlation data rather than a fixed formula.
