Hardness Conversion Calculator
Convert HRC, HRB, Vickers, Brinell HBW, and legacy HBS hardness for homogeneous non-austenitic steel using empirical ASTM E140 relationships.
Hardness conversions are approximate correlations, not exact unit conversions. Calculator is for informational purposes only. Terms and Conditions
Conversion method
Hardness scales are correlated empirically; there is no universal dimensional conversion factor.
The calculator selects the supported Rockwell C- or Rockwell B-range relation for homogeneous non-austenitic steel and numerically inverts the equation when the entered scale is the dependent variable. Modern HBW and legacy HBS are kept separate because they use different Brinell indenter bases in these ASTM relations.
Enter the known hardness
Choose the measured scale and enter the hardness number. Equivalent values update automatically.
Use this calculator for homogeneous non-austenitic carbon, alloy, and tool steels. Do not use these correlations as a substitute for the specified acceptance test.
Equivalent hardness
A primary equivalent is highlighted above; the measured scale and all supported equivalent scales appear below.
Conversion results
- Rockwell C (HRC)—
- Rockwell B (HRB)—
- Vickers (HV)—
- Brinell tungsten-carbide ball (HBW)—
- Brinell steel ball, legacy (HBS)—
Conversion applicability
Show calculation steps Review the selected correlation, inversion, range checks, and equivalent values
- Enter a valid hardness value to see the conversion steps.
Method, Sources, and Assumptions
Scope, empirical basis, limitations, and final verification requirements.
ASTM E140 states that hardness conversions are approximate and are valid only for the material classes and ranges for which the relationships were established. This calculator therefore limits the model to homogeneous non-austenitic carbon, alloy, and tool steels and keeps HBW (tungsten-carbide ball) separate from legacy HBS (steel ball).
- Conversions are empirical estimates between different indentation test methods, not exact unit conversions.
- The calculator does not extrapolate outside its verified working ranges; HBW is limited to 226–634 in this implementation.
- Rockwell C and Vickers conversions use the ASTM E140 Annex A1 non-austenitic steel equations; Rockwell B and legacy HBS use Annex A2 relations.
- Equation-based converted values can differ slightly from individual tabulated values because the Annex equations are empirical fits; converted results are rounded to whole hardness numbers.
- Converted values should not replace the specified hardness test for acceptance, certification, or specification compliance.
- Material composition, microstructure, heat treatment, surface condition, test load, and specimen geometry can change the relationship between scales.
Calculator guide
Understanding Hardness Conversion Results
The calculator above converts a known HRC, HRB, Vickers HV, Brinell HBW, or legacy HBS value into supported equivalent hardness numbers for homogeneous non-austenitic carbon, alloy, and tool steels. Choose the scale that was actually measured, enter the hardness number, and use the returned values as approximate correlations rather than exact replacements for direct testing.
Hardness conversion is different from converting inches to millimeters. Rockwell, Vickers, and Brinell tests use different indenters, force sequences, and measurement methods, so ASTM E140 treats the relationships as empirical correlations. The calculator therefore blocks unsupported ranges instead of extending an equation beyond the range used to establish it.
- Minimum input
- One measured hardness value plus its reported scale.
- Primary output
- Approximate equivalent hardness values on supported steel scales.
- Key limitation
- The implemented correlations are for homogeneous non-austenitic steels, not every metal.
Hardness Conversion Chart
The tables below show selected equation-based outputs from this calculator for the Rockwell C and Rockwell B ranges. They are quick references to the calculator behavior, not reproductions of ASTM E140 tables. Converted values are rounded to whole hardness numbers because the underlying relationships are empirical.
Rockwell C to Vickers and Brinell HBW
| Rockwell C | Vickers | Brinell HBW |
|---|---|---|
| 20 HRC | 238 HV | 226 HBW |
| 25 HRC | 267 HV | 254 HBW |
| 30 HRC | 302 HV | 287 HBW |
| 35 HRC | 342 HV | 326 HBW |
| 40 HRC | 391 HV | 370 HBW |
| 45 HRC | 448 HV | 422 HBW |
| 50 HRC | 515 HV | 483 HBW |
| 55 HRC | 595 HV | 558 HBW |
| 60 HRC | 695 HV | 661 HBW |
| 62 HRC | 744 HV | 718 HBW |
| 65 HRC | 829 HV | Not returned |
| 68 HRC | 940 HV | Not returned |
The HBW relationship extends farther into the HRC range than the earlier draft allowed, but it still stops before the full HRC-to-HV range. Once the HBW correlation is outside its supported domain, the calculator should leave that output unavailable rather than extrapolate.
Rockwell B to Vickers and legacy HBS
| Rockwell B | Vickers | Legacy HBS |
|---|---|---|
| 55 HRB | 100 HV | 100 HBS |
| 60 HRB | 107 HV | 107 HBS |
| 70 HRB | 125 HV | 125 HBS |
| 80 HRB | 150 HV | 150 HBS |
| 90 HRB | 185 HV | 185 HBS |
| 95 HRB | 210 HV | 210 HBS |
| 100 HRB | 240 HV | 240 HBS |
How ASTM E140 Hardness Conversion Works
This calculator is an empirical-correlation and numerical-inversion tool. In the Rockwell C range it uses relationships tied to non-austenitic steels, while the Rockwell B range uses separate softer-range relationships. The input scale determines which relation can be applied.
The calculator’s Conversion Range advanced option normally remains on Auto. Auto chooses the correlation branch compatible with the measured scale and hardness range. For Vickers values in the small 238–240 HV overlap, the user may explicitly compare the Rockwell B-range and Rockwell C-range relationships.
Vickers hardness to Rockwell C
Plain-language form: Rockwell C is estimated from the measured Vickers value using a nonlinear empirical fit. When HRC is the known input, the calculator solves this equation backward for HV.
The calculator restricts this relation to the implemented HRC/HV range instead of extrapolating beyond it.
Brinell HBW to Rockwell C
Plain-language form: the calculator relates Rockwell C to Brinell hardness measured with the supported tungsten-carbide-ball HBW basis, then numerically reverses the equation when HRC is known.
Vickers hardness to Rockwell B
The Rockwell B relationship is a separate softer-range correlation. The calculator does not assume that an HRC relationship remains valid merely because a numerical result could be produced.
- \(HRC\)
- Rockwell C hardness number. The scale designation is part of the result and must be retained.
- \(HRB\)
- Rockwell B hardness number for the softer-range relation used by the calculator.
- \(HV\)
- Vickers hardness number used by the implemented empirical conversion relationships.
- \(HBW\)
- Brinell hardness on the tungsten-carbide-ball basis used by the calculator’s Rockwell C relation.
ASTM E140 specifically warns that its conversion values and equations are valid only for the materials indicated. Its non-austenitic-steel tables cover homogeneous carbon, alloy, and tool steels in stated conditions, while other material families use separate relationships. That is why a steel conversion should not be automatically transferred to austenitic stainless steel, aluminum, copper, nickel alloys, or another unrelated material family.
Worked Example: 45 HRC to HV and HBW
Suppose a homogeneous non-austenitic steel is reported at 45 HRC and you need approximate Vickers and Brinell HBW equivalents for comparison. This is a reverse-conversion case because the published correlation equations express HRC as a function of HV or HBW.
Numerical conversion procedure
- Use the HRC-to-HV inverse of the implemented Vickers correlation and solve for the HV value that makes the equation equal 45 HRC.
- The numerical solution is approximately 447.64 HV, which the calculator reports as 448 HV.
- Use the HRC-to-HBW inverse of the implemented tungsten-carbide-ball Brinell correlation.
- The numerical solution is approximately 421.63 HBW, which the calculator reports as 422 HBW.
Result
45 HRC ≈ 448 HV ≈ 422 HBW
These are comparative hardness equivalents for the implemented steel correlations, not three independent hardness tests on the specimen.
How to Interpret Converted Hardness
A converted hardness value means that the applicable empirical relationship predicts a comparable reading on another hardness scale for material within the stated scope. It does not mean the two tests measure exactly the same physical response.
Preserve the scale suffix
Write 45 HRC, 448 HV, or 422 HBW—not just 45, 448, or 422. The suffix identifies the hardness method or scale and is part of the engineering meaning.
Expect a nonlinear relationship
The HRC-to-HV and HRC-to-HBW relationships are nonlinear. A fixed multiplier that happens to look reasonable at one hardness level should not be applied across the full range.
Treat missing output as information
If an equivalent is not returned, the requested relationship is outside the calculator’s supported model. That is preferable to displaying an unsupported extrapolation.
Quick sanity checks
- Verify that the known value was entered under the scale printed on the test report or material certificate.
- Check that the material is a homogeneous non-austenitic steel rather than assuming every metal uses the same conversion.
- Do not compare bare numbers across scales. For example, 60 HRC and 60 HRB do not describe the same hardness state.
- When a converted value sits close to an acceptance limit, use the specified direct test method rather than relying on conversion alone.
Rockwell vs Vickers vs Brinell
The three methods all quantify resistance to indentation, but they create and evaluate the indentation differently. That difference is the reason hardness conversion is empirical rather than a true unit conversion.
Rockwell
Rockwell hardness is an empirical indentation test based on penetration depth under a defined force sequence. HRC and HRB are different Rockwell scales with different test configurations and useful ranges.
Vickers
Vickers hardness uses a diamond indenter and evaluates the resulting indentation geometry. ASTM E92 notes that Vickers testing can reveal localized hardness variation, so one location may not represent bulk hardness.
Brinell
Brinell hardness uses a ball indenter and measures the indentation produced in the material. HBW identifies the tungsten-carbide-ball Brinell basis used by the calculator, while HBS identifies the older steel-ball basis retained for the legacy softer-range relationship.
Why the values differ
Indenter geometry, applied forces, indentation size, material response, microstructure, heat treatment, and test location can all influence how one method correlates with another.
Common Hardness Conversion Mistakes
Most serious conversion errors come from using the wrong scale, applying a steel relationship to the wrong material, or extending a correlation past its validated range.
Entering HRB as HRC
Rockwell B and Rockwell C are not interchangeable labels. If a report says 95 HRB, entering 95 as HRC changes the test meaning and is outside this calculator’s HRC input range.
Treating HB, HBW, and HBS as identical labels
Generic “HB” may hide the Brinell indenter basis. This calculator separates tungsten-carbide-ball HBW from the legacy steel-ball HBS relationship because the equations are not the same.
Using one conversion for every metal
ASTM E140 contains separate relationships for different material families. A non-austenitic steel conversion should not be assumed valid for austenitic stainless steel, aluminum, copper, or nickel alloys.
Extrapolating because the equation still returns a number
A polynomial can continue producing numbers outside its fitted range. That does not make those numbers valid hardness equivalents. The calculator blocks unsupported input and output regions for this reason.
Comparing scale numbers directly
A larger numerical value on HV than on HRC does not mean the Vickers test found a “harder” material. The scales use different numerical definitions.
Using conversion to settle an acceptance dispute
When a contractual requirement specifies a test method or scale, verify the actual requirement before substituting a converted result. ASTM E140 describes converted values as approximate comparative estimates.
Assumptions and Limits
The calculator is deliberately narrower than the full ASTM E140 standard. Its implemented equations cover selected non-austenitic-steel relationships and use strict numerical ranges to avoid unsupported extrapolation.
Material family
Use the implemented conversions for homogeneous non-austenitic carbon, alloy, and tool steels within the supported conditions and ranges. Other material families require their own applicable correlations.
Hardness is local
ASTM E18, E10, and E92 all emphasize that a test at one location may not represent an entire component. Case depth, decarburization, gradients, local microstructure, and surface condition can matter.
Conversion uncertainty is not a fixed percentage
ASTM E140 explains that the various hardness methods do not measure the same combination of material properties and that broad universal confidence limits for conversion error cannot be stated.
HBW output has a practical model boundary
The calculator does not return HBW across the entire 20–68 HRC range. The implemented tungsten-carbide-ball HBW relation extends through approximately the low-60s HRC range; once its supported HBW domain is exceeded, the result remains unavailable instead of being extrapolated.
Can Hardness Be Converted to Tensile Strength?
Hardness can sometimes be correlated empirically with tensile strength for particular metals and conditions, but hardness is not a tensile test and there is no universal hardness-to-strength conversion that is valid for every alloy, heat treatment, or microstructure.
ASTM E18 notes that Rockwell hardness may correlate with tensile strength and other material properties, but the relationship is empirical. If tensile strength is a governing design or acceptance value, use a material-specific correlation only when the governing specification permits it, and rely on direct tensile-test data when required.
Sources and Calculation Basis
The calculator and guide use ASTM E140 as the hardness-conversion basis and current ASTM test-method pages for the meaning and limitations of the individual Rockwell, Brinell, and Vickers methods. The worked example was independently reverse-checked by substituting both solved equivalents back into the calculator equations.
- ASTM E140-12B(2019)e1 — Standard Hardness Conversion Tables for Metals — Supports the material-specific, approximate nature of hardness conversion and the separate non-austenitic-steel Rockwell C and Rockwell B conversion scopes.
- ASTM E18-25 — Rockwell Hardness of Metallic Materials — Supports Rockwell hardness as an empirical indentation test and the caution that a local hardness reading may not represent the whole part.
- ASTM E10-23 — Brinell Hardness of Metallic Materials — Supports the Brinell indentation-hardness method and the limitation that a local Brinell result may not represent the entire component.
- ASTM E92-23 — Vickers and Knoop Hardness of Metallic Materials — Supports the Vickers indentation-hardness method and the possibility of local hardness variation within a material.
- NIST SP 960-5 — Rockwell Hardness Measurement of Metallic Materials — Provides open technical guidance on Rockwell measurement practice, sources of variability, and scale use.
This page does not reproduce ASTM conversion tables. The reference charts above contain selected values generated from the calculator’s implemented empirical equations, so users can verify the behavior of this specific tool and understand why an equation result may differ slightly from a published table row.
Hardness Conversion FAQs
These answers address the conversion questions that commonly accompany HRC, HRB, HV, and Brinell hardness lookups.
How do you convert HRC to HV?
For supported non-austenitic steels, use an applicable empirical relationship rather than a fixed multiplier. This calculator numerically solves the implemented ASTM E140-based HRC/HV correlation in reverse when HRC is the known value.
What is 45 HRC in Vickers hardness?
Using this calculator’s implemented equation, 45 HRC corresponds to approximately 447.64 HV, displayed as 448 HV. That is an approximate comparative conversion for the stated non-austenitic-steel scope.
What is 45 HRC in Brinell hardness?
Using the implemented tungsten-carbide-ball Brinell relationship, 45 HRC corresponds to approximately 421.63 HBW, displayed as 422 HBW.
Is there an exact formula for HRC to HV?
No universal exact conversion applies to every material. ASTM E140 describes hardness conversion as approximate and material-specific. Equations can represent particular empirical relationships within defined ranges, but those relationships should not be generalized beyond their scope.
Why does the calculator sometimes show no HBW equivalent?
The implemented HBW relationship does not cover every HRC value that the HRC/HV relationship covers. When HBW is outside the supported range, the calculator leaves that conversion unavailable rather than extrapolating.
What is the difference between HBW and HBS?
HBW denotes the tungsten-carbide-ball Brinell basis used by the calculator’s harder Rockwell C relationship. HBS is the legacy steel-ball Brinell basis used by the calculator’s softer Rockwell B relationship. They should not be treated as interchangeable labels inside the calculation.
Can I use this steel conversion for stainless steel?
Do not assume so. The calculator is scoped to homogeneous non-austenitic carbon, alloy, and tool steels. ASTM E140 provides separate material-specific relationships for other material families, and austenitic stainless steels are not covered by this calculator’s steel model.
Is a converted hardness acceptable for a specification?
That depends on the governing specification or agreement. ASTM E140 emphasizes the approximate nature of conversion and recommends avoiding conversion of test data when possible. If acceptance is tied to a named test scale or method, verify the requirement and use the specified direct test where required.
How do you convert HV to HRC?
Enter the measured Vickers value as HV and let the calculator evaluate the applicable non-austenitic-steel correlation. In the small 238–240 HV overlap, the advanced Conversion Range option can be used to compare the Rockwell B-range and Rockwell C-range relationships.
How do you convert HBW to HRC?
Choose Brinell HBW as the measured scale, enter the tungsten-carbide-ball Brinell value, and use the returned Rockwell C equivalent only when the value falls within the supported non-austenitic-steel HBW correlation range.
What is the difference between HRC and HRB?
HRC and HRB are different Rockwell hardness scales. HRC uses a diamond indenter and is commonly used for harder metallic materials, while HRB uses a ball indenter for softer ranges. A value such as 90 HRB cannot be read as 90 HRC.