Hardness Conversion Calculator
Convert hardness conversion between units instantly. Includes conversion tables, common equivalents, and calculation formulas.
Reviewed for accuracy by Manoj Kumar, Mathematics Educator
Hardness Conversion Calculator
Calculator
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Formula: HV = 1.761 x HRC^2 - 50.82 x HRC + 1444.5; HB = 0.92 x HV + 4.2
Worked example — 60 HRC = 697.1 HV = 645.5 HB = 2166 MPa tensile
Formula
HV = 1.761 x HRC^2 - 50.82 x HRC + 1444.5; HB = 0.92 x HV + 4.2
Hardness conversions use polynomial approximations derived from ASTM E140 standard tables for steel. Vickers hardness is calculated from Rockwell C using a quadratic fit. Brinell is estimated from Vickers using a linear relationship. Approximate tensile strength in MPa equals 3.09 times Vickers hardness plus 12.5. These conversions are most accurate for carbon and alloy steels.
Worked Examples
Example 1: Converting HRC to Vickers and Brinell
Problem:Convert 60 HRC to Vickers (HV) and Brinell (HB) hardness.
Solution:HV = 1.761 x 60^2 - 50.82 x 60 + 1444.5 HV = 6339.6 - 3049.2 + 1444.5 = 697.1 HV HB = 0.92 x 697.1 + 4.2 = 645.5 HB Tensile = 3.09 x 697.1 + 12.5 = 2166 MPa
Result:60 HRC = 697.1 HV = 645.5 HB = 2166 MPa tensile
Example 2: Converting Brinell to Other Scales
Problem:Convert 300 HB (Brinell) to HRC and HV.
Solution:HV = (300 - 4.2) / 0.92 = 321.5 HV HRC: solve 1.761x^2 - 50.82x + (1444.5 - 321.5) = 0 HRC = 32.5 (approximate) Tensile = 3.09 x 321.5 + 12.5 = 1006 MPa
Result:300 HB = 321.5 HV = 32.5 HRC = 1006 MPa tensile
Frequently Asked Questions
What are the main hardness scales and when are they used?
The three primary scales are Rockwell (HRC/HRB), Vickers (HV), and Brinell (HB). Rockwell C (HRC) is most common for hardened steels with a range of 20-70 and uses a diamond cone indenter. Vickers uses a diamond pyramid and works across all hardness levels, making it ideal for thin materials and case-hardened surfaces. Brinell uses a steel or tungsten carbide ball and is preferred for castings, forgings, and softer materials. Each scale measures resistance to permanent indentation under specific test conditions.
How accurate are hardness scale conversions?
Hardness conversions are approximate because different tests measure different physical properties. ASTM E140 provides standard conversion tables specifically for steel, and these are accurate to within about 2-5% for most common ranges. Conversions become less reliable at extreme values and for non-steel materials. Aluminum, brass, and titanium have different elastic properties that affect the relationship between scales. For critical applications, always perform the actual hardness test in the required scale rather than relying on conversions.
What is the relationship between hardness and tensile strength?
For carbon and alloy steels, an approximate linear relationship exists between Vickers hardness and ultimate tensile strength: tensile strength in MPa is roughly 3.09 times the Vickers hardness number. This relationship holds reasonably well for steels in the HRC 20-55 range. Above HRC 55, steels become brittle and the correlation weakens. For non-ferrous metals, the relationship is different and depends heavily on the specific alloy and heat treatment condition.
Why do different hardness tests give different numbers for the same material?
Each hardness test uses a different indenter geometry, applied load, and measurement method, so the resulting numbers represent different physical quantities. Rockwell measures indentation depth, Vickers and Brinell measure indentation area. A 60 HRC steel has a Vickers hardness around 697 and a Brinell of about 645, but these all describe the same material. The scales were developed for different applications and industries, leading to parallel systems that persist due to established standards and equipment investments.
What hardness values are typical for common applications?
Mild structural steel measures about 120-180 HB (equivalent to roughly 10-15 HRC). Automotive gears and shafts are typically 58-62 HRC after hardening. Cutting tools and drill bits range from 60-68 HRC. Knife blades are usually 55-62 HRC, with higher values giving better edge retention but more brittleness. Bearing steel (52100) runs at 60-64 HRC. Stainless steel varies widely from 150 HB for austenitic grades to 60 HRC for martensitic grades used in surgical instruments.
How do significant figures affect unit conversions?
Your converted result should have the same number of significant figures as your original measurement. If you measure 5.2 inches (2 significant figures), converting to centimeters gives 13 cm, not 13.208 cm. Using excessive decimal places implies false precision.
What are the most common unit conversion mistakes?
Common errors include confusing fluid ounces with weight ounces, mixing up miles and nautical miles, forgetting that UK and US gallons differ (UK is 20% larger), using the wrong temperature formula, and not accounting for the difference between troy and avoirdupois ounces.
How precise should my unit conversions be?
Match precision to your application. Cooking tolerates rough conversions (1 cup is about 240 mL). Engineering may need 4-6 decimal places. Scientific work requires exact conversion factors and proper significant figure handling. More precision than your measurement accuracy is meaningless.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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