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Hardness Converter - ASTM E140 HRC/HRB/HB/HV & Tensile Strength Conversion

Convert between Rockwell C, Rockwell B, Brinell, Vickers, and approximate tensile strength per ASTM E140

Convert hardness values between Rockwell C (HRC), Rockwell B (HRB), Brinell (HBW 10/3000), Vickers (HV), Knoop (HK), and approximate ultimate tensile strength (ksi/MPa) using ASTM E140 Standard Hardness Conversion Tables for metals. Enter any one hardness value and get equivalent values on all other scales. Covers non-austenitic steels, tool steels, and carbon/alloy steels. Includes hardness range validation, scale selection guidance, and material condition reference for common steel grades.

Pro Tip: ASTM E140 conversions are only valid for non-austenitic steels. Converting hardness for stainless steel, aluminum, copper alloys, or cast iron using these tables gives inaccurate and misleading results. For those materials, you need material-specific correlation data from the manufacturer or ASTM E140 Table 3 (nickel alloys) or Table 4 (copper alloys). The most common mistake in hardness testing is applying the wrong conversion table to the wrong material.

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Material Hardness Converter
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How It Works

  1. Select Input Scale

    Choose the hardness scale of your measurement: Rockwell C (HRC, 20-70 range), Rockwell B (HRB, 0-100 range), Brinell (HBW, 75-750 range), or Vickers (HV, 75-1000+ range). Each scale has a specific load and indenter type that determines its valid range.

  2. Enter Your Hardness Value

    Input the measured hardness value. The calculator validates that the value falls within the standard range for the selected scale and warns if the value is outside the reliable conversion range per ASTM E140.

  3. Review Converted Values

    See equivalent hardness on all other scales plus approximate ultimate tensile strength in ksi and MPa. Values are interpolated from ASTM E140 Table 1 data for non-austenitic steels. Cells are grayed out where the conversion is outside the valid range for that scale.

  4. Check Material Reference

    Compare your hardness value to typical ranges for common steel conditions: annealed (150-200 HB), normalized (170-250 HB), quenched and tempered (250-550 HB), case hardened surface (58-65 HRC), and through-hardened tool steel (45-65 HRC).

Built For

  • Quality inspectors verifying material hardness meets specification requirements after heat treatment
  • Millwrights and machinists selecting cutting tools and feeds based on workpiece hardness
  • Welding engineers evaluating heat-affected zone hardness for NACE and ASME code compliance
  • Metallurgists correlating hardness test results across different testing methods and labs
  • Purchasing agents verifying material certifications against hardness specifications on purchase orders
  • Maintenance techs field-testing shaft, gear, and bearing hardness with portable testers
  • Failure analysts correlating component hardness to tensile strength for root cause determination

Features & Capabilities

ASTM E140 Table 1 Data

All conversions use the official ASTM E140 Standard Hardness Conversion Tables for Metals (Table 1 for non-austenitic steels). Data is interpolated between table entries for values that fall between standard data points. No empirical formulas or approximations that deviate from the standard.

Five-Scale Conversion

Converts between Rockwell C (HRC), Rockwell B (HRB), Brinell 10/3000 (HBW), Vickers (HV), and Knoop (HK). Also provides approximate ultimate tensile strength (UTS) in both ksi and MPa for carbon and alloy steels within the valid range.

Range Validation

Validates input values against the standard range for each scale and flags out-of-range entries. HRC is valid from 20 to 68, HRB from 0 to 100, Brinell from 75 to about 739 (for 10mm ball, 3000 kgf). Results outside the reliable conversion zone are clearly marked.

Tensile Strength Approximation

Provides approximate ultimate tensile strength correlated to hardness per ASTM E140. This correlation is only valid for non-austenitic steels in the wrought condition. The approximation is most accurate in the 120-450 HB range and becomes less reliable at extreme hardness values.

Comparison

Hardness Scale Indenter Load Typical Range Best Application
Rockwell C (HRC) 120° diamond cone 150 kgf 20-68 HRC Hardened steels, tool steels, case hardening
Rockwell B (HRB) 1/16" steel ball 100 kgf 0-100 HRB Annealed steel, brass, aluminum (softer metals)
Brinell (HBW) 10mm tungsten carbide ball 3000 kgf 75-750 HB Castings, forgings, raw stock, large parts
Vickers (HV) 136° diamond pyramid 1-120 kgf 75-1000+ HV All metals, thin sections, micro-hardness
Knoop (HK) Elongated diamond 0.025-5 kgf 100-1000+ HK Micro-hardness, coatings, thin layers, brittle materials

Frequently Asked Questions

HRC (Rockwell C) uses a diamond cone indenter at 150 kgf load and measures hardened steels from 20 to 68 HRC. HRB (Rockwell B) uses a 1/16-inch steel ball indenter at 100 kgf load and measures softer metals from 0 to 100 HRB. If your steel is hardened above about 240 HB (or roughly 100 HRB), switch to the C scale. If it is annealed or normalized below about 240 HB, use the B scale. Using the wrong scale gives unreliable readings.
ASTM E140 conversions are approximate, with typical accuracy of plus or minus 1-2 HRC points or plus or minus 10-15 HB points for non-austenitic steels. The conversions are empirical correlations, not exact mathematical relationships, because each hardness test measures a different physical property (depth vs. area of indentation). Conversions are most accurate in the mid-range of each scale and less reliable at the extremes.
ASTM E140 Table 1 applies only to non-austenitic steels (carbon, alloy, and tool steels). Austenitic stainless steels (304, 316) work-harden differently and the standard conversion tables do not apply. ASTM E140 includes separate tables for specific material groups: Table 2 for austenitic steels, Table 3 for nickel alloys, and Table 4 for copper alloys. For aluminum, use material-specific data from the aluminum association or the alloy producer.
For carbon and alloy steels, a rough approximation is UTS (psi) = 500 x HB (for HB up to about 400). So a steel at 200 HB has an approximate UTS of 100,000 psi (100 ksi). This is a widely used rule of thumb in industry, though the actual ASTM E140 correlation varies slightly from the 500x multiplier. The correlation breaks down for very hard steels (above 400 HB) and does not apply to non-ferrous metals at all.
Use Brinell (HBW) for castings, forgings, and raw stock where the large indentation averages out microstructural variations. Brinell is also required by many material specifications (ASTM A36, A572, etc.). Use Rockwell for finished and heat-treated parts where the smaller indentation is less destructive. Rockwell is faster (direct reading) and better suited for production testing. Vickers is used when neither Brinell nor Rockwell are practical, such as thin sections and weld HAZ testing.
Portable testers (Leeb rebound, UCI ultrasonic) measure a different physical property than standard bench testers and convert to HRC/HRB/HB using built-in algorithms. Accuracy depends on surface finish (must be ground smooth), coupling gel application, part mass (small or thin parts give false readings), and calibration. Portable testers are convenient for field work but are not substitutes for bench-mounted Rockwell or Brinell testers for acceptance testing per material specifications.
Quenched and tempered carbon and alloy steels typically range from 25 to 55 HRC (250-550 HB) depending on carbon content, alloy additions, and tempering temperature. AISI 4140 tempered at 800 degrees F is typically 38-42 HRC. AISI 4340 tempered at 600 degrees F is typically 48-52 HRC. Higher tempering temperatures reduce hardness but improve toughness. The specific hardness specification depends on the application requirements.
Disclaimer: This converter uses ASTM E140 Standard Hardness Conversion Tables for non-austenitic steels. Conversions are approximate and may not be accurate for austenitic stainless steels, aluminum, copper alloys, cast iron, or non-metallic materials. Tensile strength approximations are valid only for carbon and alloy steels in the wrought condition. Always verify critical hardness requirements using the test method specified in the applicable material standard.

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