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Hardness Scale Converter

Science

Convert between Rockwell (B/C), Brinell, Vickers, Shore D, and Mohs hardness scales using standard approximate steel conversion tables instantly.

Reviewed by the thecalcu.com team · Last updated July 23, 2026

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What is a Hardness?

The Hardness Scale Converter converts material hardness values between Rockwell (B and C scales), Brinell, Vickers, Shore D, and Mohs. Unlike converting between metres and feet, hardness scales don't relate through a fixed mathematical formula, each test method (Rockwell, Brinell, Vickers) applies a different indenter shape and load, producing results that only correlate empirically, not linearly, across the full hardness range. Materials science and manufacturing standards address this with published correlation tables (closely following ASTM E140), and that's exactly what this converter interpolates against.

Enter a value in any supported scale and the converter estimates its equivalent in any other, using a standard steel-based correlation table. For force- or pressure-related physics conversions in the same CGS/SI vein, see the CGS to SI Units Converter.

Why Use a Hardness Scale Converter?

Material spec sheets, quality control reports, and supplier documentation don't always agree on which hardness scale to use, a heat-treated steel part might be specified in Rockwell C, while an incoming inspection report measures it in Brinell, and a plastic component nearby is rated in Shore D. Manually cross-referencing a printed ASTM E140 table for every conversion is slow and error-prone, especially when working across several material types in one session.

This converter puts the standard correlation data behind a single input field, so a quality engineer or student can move between scales instantly. Because hardness testing connects closely to a material's mechanical strength, this pairs naturally with the Density Converter when characterising a material fully.

Who Should Use This Converter?

  • Materials and quality engineers cross-referencing hardness values reported in different scales across supplier certificates, inspection reports, and internal specs.
  • Metallurgy and mechanical engineering students learning to interpret Rockwell, Brinell, and Vickers hardness test results and how they relate to each other.
  • Machinists and toolmakers checking whether a heat-treated part's Rockwell C rating matches the Brinell or Vickers spec on an older drawing.
  • Geology and mineralogy students comparing the Mohs scratch-hardness scale against indentation-hardness values for context.
  • Manufacturing QA teams working with mixed-material assemblies that combine metal (Rockwell/Brinell/Vickers) and polymer (Shore D) components.

What Insights Does the Hardness Converter Give You?

The main output is the converted hardness value in your chosen target scale, calculated by interpolating your input against a standard steel-based correlation table (Vickers is used as the internal reference point every other scale converts through). Because the underlying table is empirical rather than formulaic, precision decreases somewhat toward the extreme ends of each scale, treat results near the table boundaries as approximate.

For the Mohs scale specifically, remember it measures a fundamentally different property (scratch resistance between minerals) rather than indentation depth, so its correlation to Vickers is a widely used approximation for general comparison, not a precise engineering equivalence.

How to use this Hardness calculator

  1. Choose your starting scale from the source dropdown, for example, "Rockwell C (HRC)".
  2. Enter the hardness value you want to convert in the input field.
  3. Choose your target scale from the destination dropdown, for example, "Vickers (HV)".
  4. Read the converted result, which updates instantly as you type or change scales.
  5. Use the swap (⇅) button to reverse the conversion direction.
  6. Use the copy button to grab the result for a report, spec sheet, or inspection record.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The converter uses Vickers (HV) as its internal reference scale. Every other scale (Rockwell C, Rockwell B, Brinell, Shore D, Mohs) is mapped to Vickers through a table of published approximate equivalence points, and conversions between two non-Vickers scales pass through Vickers as an intermediate step.

Values falling between two table points are calculated by linear interpolation:

Result = Value at lower point + (Input − Lower boundary) ÷ (Upper boundary − Lower boundary) × (Value at upper point − Value at lower point)

Values outside the table's range are clamped to the nearest endpoint rather than extrapolated, since hardness correlations are unreliable beyond their tested range.

Worked example, converting 50 Rockwell C to Vickers:

The table brackets 50 HRC between the points (49 HRC, 500 HV) and (52 HRC, 550 HV). Interpolating: 500 + (50 − 49) ÷ (52 − 49) × (550 − 500) = 500 + 0.333 × 50 ≈ 517 HV

This falls within the commonly cited approximate range for 50 HRC steel (roughly 480–520 HV depending on the specific reference table used).

For background on the underlying term, see our glossary entry on Vickers Hardness.

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Frequently Asked Questions

What is the difference between Rockwell, Brinell, and Vickers hardness scales?
All three measure resistance to indentation but use different indenters and load ranges, Rockwell (a diamond cone or steel ball) reads hardness directly off the machine's depth measurement, Brinell (a hardened steel or carbide ball) measures the diameter of the resulting indent, and Vickers (a diamond pyramid) measures the indent's diagonal length. Each is suited to different material hardness ranges and specimen sizes, which is why conversion between them is needed so often in materials engineering.
How do I convert Rockwell C to Vickers?
Enter your Rockwell C (HRC) value with 'Rockwell C (HRC)' as the source unit and 'Vickers (HV)' as the target, the converter interpolates your value against a standard approximate steel equivalence table. For example, 50 HRC converts to approximately 513 HV.
Is hardness scale conversion exact?
No, hardness scale conversions are empirical approximations based on standardised correlation tables (closely following ASTM E140), not fixed mathematical formulas, and they're calibrated primarily for steel. Results for other materials (aluminium, brass, plastics) can deviate meaningfully from the steel-based table this converter uses.
Why can't hardness scales be converted with a simple formula?
Different hardness tests apply different loads, use different indenter shapes, and measure different physical responses (depth versus indent diameter versus indent diagonal), so the relationship between scales isn't linear or universally consistent across all hardness ranges and materials. Standards bodies publish empirical correlation tables built from measuring the same specimens with multiple test methods, which is what this converter's interpolation is based on.
What is Rockwell B used for versus Rockwell C?
Rockwell B (HRB) is used for softer materials like unhardened steel, aluminium, and brass, using a lower test load and a steel ball indenter, while Rockwell C (HRC) is used for harder materials like hardened steel and tool steel, using a heavier load and a diamond cone indenter. This converter includes both scales, and the table is populated only where each scale is metallurgically meaningful.
What is the Mohs scale, and how does it relate to Vickers hardness?
The Mohs scale is a 1-to-10 ordinal ranking of minerals based on which one can scratch another, it measures scratch resistance, not indentation hardness like Rockwell, Brinell, or Vickers do. The approximate Vickers-to-Mohs mapping in this converter is a widely cited reference for comparing mineral hardness to metal hardness, but treat it as a rough comparison rather than a precise engineering conversion.
What is Shore D hardness used for?
Shore D measures the hardness of hard plastics, hard rubbers, and some softer metals using a spring-loaded indenter that reads a value directly, without needing a separate measurement step. It's commonly referenced alongside Rockwell and Brinell in material spec sheets that span both metal and polymer components.
How accurate is this converter for non-steel materials?
The core Rockwell/Brinell/Vickers/Shore D table is calibrated for steel, since that's what standardised hardness correlation tables are built around, using it for aluminium, titanium, or other alloys will give an approximate result at best, and for polymers or ceramics, the deviation can be significant. For critical engineering or quality-control decisions on non-steel materials, always use the specific correlation data published for that material.
How do I convert Brinell to Rockwell C?
Enter your Brinell (HB) value with 'Brinell (HB)' as the source unit and 'Rockwell C (HRC)' as the target, the converter first resolves your Brinell value to its Vickers equivalent internally, then converts that to Rockwell C. This two-step chain through Vickers keeps every possible unit pair consistent.
What happens if I enter a hardness value outside the standard table range?
Values below or above the table's covered range are clamped to the nearest endpoint rather than extrapolated, since hardness correlation tables become unreliable outside their tested range. If your value is near the edge of a very hard or very soft material, treat the result as a rough estimate and consult a full ASTM E140 reference table if precision matters.
Also known as
rockwell to vickersbrinell to rockwell chardness conversion chartmohs to vickers hardnessrockwell c to brinellhardness scale chart