Hardness Conversion Calculator
Convert hardness conversion between units instantly. Includes conversion tables, common equivalents, and calculation formulas.
Hardness Conversion Calculator
Calculator
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Formula: 60 HRC = 697 HV = 654 HB | 50 HRC = 513 HV = 481 HB | 40 HRC = 392 HV = 371 HB | Tensile (MPa) = 3.09 x HV + 12.5
Worked example — 60 HRC = 697 HV = 654 HB (tensile roughly 2,166 MPa)
Formula
60 HRC = 697 HV = 654 HB | 50 HRC = 513 HV = 481 HB | 40 HRC = 392 HV = 371 HB | Tensile (MPa) = 3.09 x HV + 12.5
There is no algebraic formula linking hardness scales, because each test measures a different physical quantity: Rockwell C reads indentation depth, while Vickers and Brinell read indentation area. Conversions are therefore table lookups. This calculator interpolates ASTM E140 Table 1, the standard approximate conversion table for non-austenitic steels over the 20-68 HRC range, so 60 HRC returns 697 HV and 654 HB. Brinell stops at 65 HRC (739 HB) because the ball indenter itself deforms above that. Tensile strength is a separate empirical estimate, roughly 3.09 MPa per Vickers point, and it loses accuracy above about 55 HRC.
Worked Examples
Example 1: Converting HRC to Vickers and Brinell
Problem:Convert 60 HRC to Vickers (HV) and Brinell (HB) hardness.
Solution:Read the 60 HRC row straight from ASTM E140 Table 1: HV = 697 (Vickers) HB = 654 (HBW 10/3000 tungsten carbide ball) Tensile estimate = 3.09 x 697 + 12.5 = 2,154 + 12.5 = 2,166 MPa Above about 55 HRC the hardness-to-tensile correlation weakens, so treat 2,166 MPa as an order-of-magnitude figure only.
Result:60 HRC = 697 HV = 654 HB (tensile roughly 2,166 MPa)
Example 2: Converting Brinell to Other Scales
Problem:Convert 300 HB (Brinell) to HRC and HV.
Solution:300 HB sits between the 294 HB (31 HRC, 310 HV) and 301 HB (32 HRC, 318 HV) rows of ASTM E140 Table 1, so interpolate: Fraction = (300 - 294) / (301 - 294) = 0.857 HRC = 31 + 0.857 x 1 = 31.9 HV = 310 + 0.857 x 8 = 316.9 Tensile estimate = 3.09 x 316.9 + 12.5 = 979.2 + 12.5 = 992 MPa
Result:300 HB = 31.9 HRC = 317 HV (tensile roughly 992 MPa)
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 of about 697 and a Brinell of about 654, 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 is a Rockwell C measurement actually taken?
The Rockwell C scale uses a 120-degree spheroconical diamond indenter known as a brale. A 10 kgf minor load seats the indenter and zeroes the depth gauge, then a 150 kgf major load is applied and removed, and the machine reads the permanent increase in depth that remains under the minor load. Each HRC point corresponds to 0.002 millimetres of that residual depth, so the number is a depth measurement rather than an area measurement. Because it reads depth directly and needs no optical measurement, the test is fast, which is why it dominates production heat-treat control.
What is the difference between the Vickers and Knoop microhardness tests?
Both press a diamond pyramid and compute hardness from the measured diagonals, but the geometry differs. Vickers uses a square-based pyramid with 136-degree face angles and reports HV from the mean diagonal, giving one continuous scale from soft metals to carbides. Knoop uses an elongated rhombic pyramid with included angles of 172.5 and 130 degrees, producing a long, shallow indent measured on its major diagonal. That shallowness makes Knoop better for thin coatings, brittle ceramics and readings close to an edge, where a Vickers indent would crack or punch through.
Why must a Brinell result state the indenter diameter and load?
Brinell hardness is the applied load divided by the curved surface area of the indent, so the same material yields different numbers if the ball size or load changes. That is why results are written as, for example, 250 HBW 10/3000, meaning a 10 mm tungsten carbide ball under 3,000 kgf. Comparability between setups depends on keeping the load-to-diameter-squared ratio constant for a given material class, so indents stay geometrically similar. A bare Brinell number without its test conditions is ambiguous, and any conversion made from it is unreliable.
When is a portable Leeb rebound tester the right choice?
Leeb testing fires a small impact body at the surface and derives hardness from the ratio of rebound velocity to impact velocity, so it works on parts too large or too fixed to bring to a bench machine, such as castings, rolls, shafts and installed structures. The catch is that the raw HL value depends strongly on the part's mass, stiffness and surface finish, and converting it to HB or HRC needs a material-specific correlation. Light or thin parts must be coupled to a heavy support, otherwise the reading falls low because the part itself moves and absorbs energy.
How does case hardening change which hardness scale you should use?
A carburised or nitrided part has a hard skin over a much softer core, and a heavy indentation can punch through the case so the reading reflects the substrate instead. Case depth therefore governs scale choice: superficial Rockwell scales such as 15N, 30N and 45N use a 3 kgf minor load and lighter major loads to stay shallow, while microhardness traverses with Vickers or Knoop on a polished cross-section map hardness against depth. Deep-case parts can usually take standard HRC; thin nitrided layers cannot.
References
Reviewed for accuracy by Manoj Kumar, Mathematics Educator · Editorial policy
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