Hardness Conversion Calculator

About the Hardness Conversion Calculator

Material hardness — resistance to indentation or scratching — is measured on several different scales depending on the application. The Vickers (HV) and Brinell (HB) tests use indentation depth, Rockwell (HRC, HRB) uses a combination of depth and load, and Mohs measures scratch resistance on a 1-10 scale. Engineers, metallurgists, and gemologists frequently need to convert between these scales.

It gives approximate conversions between five major hardness scales: Vickers, Brinell, Rockwell C, Rockwell B, and Mohs. Enter a hardness value in any scale and see equivalents in all others. The log-scale hardness bar provides visual context, and presets load common material hardnesses (mild steel, hardened steel, glass, diamond).

Note that hardness conversions are inherently approximate — different scales measure different physical properties and exact conversion depends on the material. The conversions here follow standard ASTM E140 approximations valid for typical steel and metal alloys. It helps teams compare test reports faster when different suppliers use different hardness scales.

When This Page Helps

Engineers and metallurgists often receive hardness values in different scales from different labs, suppliers, and standards documents. It gives practical ASTM-based approximations across Vickers, Brinell, Rockwell, and Mohs so teams can compare materials quickly, communicate limits clearly, avoid manual lookup errors during specification reviews, and make faster quality decisions with shared reference values.

How to Use the Inputs

1. Select the hardness scale you are converting from.
2. Enter the hardness value.
3. View approximate equivalents in all five scales.
4. Use presets for common materials (mild steel, hardened steel, glass, diamond).
5. Check the log-scale bar for visual hardness context.
6. Expand the reference table for standard material hardness values.

Example Calculation

Tips & Best Practices

• Rockwell C (HRC) is valid mainly above 20 HRC — conversions below this range are unreliable.
• Brinell is best for softer metals; Vickers works across the full hardness range.
• Mohs is ordinal (not linear) — the jump from Mohs 9 to 10 is much larger than from 1 to 2.
• For precise work, always test hardness directly in the required scale rather than converting.
• ASTM E140 is the standard for hardness conversion tables; these calculations follow it approximately.
• Rockwell B uses a steel ball indenter (softer materials); Rockwell C uses a diamond cone (harder materials).

Understanding Hardness Scales

Vickers (HV): A diamond pyramid indenter pressed into the surface; hardness = load/impression area. Range: 10-10000+ HV. Used universally for metals and ceramics. Brinell (HB): A hard steel or carbide ball pressed into the surface. Range: 1-700 HB. Preferred for castings and raw materials. Rockwell C/B: Measures depth of indentation under two loads. C scale (diamond cone) for hard materials; B scale (steel ball) for softer ones.

ASTM E140 Standard

The American Society for Testing and Materials publishes E140, the standard conversion table for metals. These tables are empirical — derived from testing the same materials on multiple scales. The conversions in this calculator follow ASTM E140 approximations.

Hardness in Practice

Knife makers select steel and heat treatment to achieve specific HRC values. Gemologists use Mohs to classify gem durability. Manufacturers spec minimum hardness for wear resistance. Quality control departments verify incoming materials against purchase specifications using portable hardness testers.

Frequently Asked Questions

• Are hardness conversions exact?

  No. Different hardness tests measure different properties (indentation depth, scratch resistance), so conversions are approximate. They are valid within specific material ranges, primarily carbon and alloy steels.

• What is the difference between Vickers and Brinell?

  Vickers uses a diamond pyramid indenter with a light load (good for thin materials and hard coatings). Brinell uses a large steel ball (good for castings and forgings). For steel in the 100-400 HB range, HV ≈ HB × 1.05.

• When should I use Rockwell C vs Rockwell B?

  Rockwell C (HRC) is for hard materials like hardened steel (20-70 HRC). Rockwell B (HRB) is for softer materials like brass, copper, and annealed steel (0-100 HRB).

• What does Mohs hardness measure?

  Mohs measures scratch resistance on a 1-10 scale where each mineral can scratch all those below it. It is ordinal — the difference between Mohs 9 (corundum, HV 2000) and 10 (diamond, HV 10000) is enormous.

• What hardness is typical for tool steel?

  Hardened tool steel is typically 58-65 HRC (650-830 HV). Knife blades are usually 56-62 HRC.

• Can I convert Mohs to Vickers accurately?

  Only roughly — Mohs is an ordinal scale, not a ratio scale. The relationship is approximately logarithmic. For engineering work, use Vickers or Brinell directly.