Hardness Conversion Calculator: Brinell, Vickers, Knoop, Shore and Mohs
Convert hardness between Brinell (HB), Vickers (HV), Knoop (HK), Shore A/D, and Mohs. Includes Brinell, Vickers, and Knoop test calculators, a chart, and inline reference tables for material selection and QA/QC. All cross-scale values are empirical approximations.
Scope: non-Rockwell scales
This tool covers the non-Rockwell hardness scales: Brinell, Vickers, Knoop, Shore (durometer), and Mohs. For Rockwell C/B/A conversions, see our Rockwell Hardness Converter, which is built on the full ASTM E140 Rockwell tables.
Hardness scale converter
Enter a value, pick its scale, and get the approximate equivalents. Conversions between HV, HB, and HK use the empirical steel table; Shore A/D use the durometer overlap chart; Mohs uses mineral equivalents. Shore durometer has no empirical conversion to the metal scales, so those cells report as not convertible instead of guessing.
Worked examples: 300 HB is approximately 317 HV; 500 HV is approximately 528 HK; Shore A 95 is approximately Shore D 46; quartz at Mohs 7 is approximately 1160 HV.
Vickers vs Brinell and Knoop chart
Steel-scale curves from the empirical table. The dashed marker follows your converted value.
Brinell hardness calculator
Computes HB from the test parameters using the ISO 6506 / ASTM E10 definition: HB = 2F / (πD(D − √(D² − d²))). The impression diameter should fall between 0.24D and 0.6D for a valid test.
HB from load and impression
Plan a test: required impression for a target HB
Standard F/D² ratios (ISO 6506): 30 for steels and cast iron (e.g. 10 mm / 3000 kgf), 10 for copper alloys, 5 for aluminium alloys, 2.5 and below for soft metals.
Vickers and Knoop calculators
Direct test calculations per ASTM E92. Vickers: HV = 1.8544 × F / d² with the mean diagonal. Knoop: HK = 14.229 × F / d² with the long diagonal. F in kilogram-force, d in millimetres.
Vickers HV
Knoop HK
Hardness conversion reference tables
All values approximate. The steel table is interpolated from published ASTM E140 data points for non-austenitic steels; values marked * are the bracketed practical approximations the standard itself gives above the strict Brinell range. Tensile strength applies to carbon and low-alloy steels only.
Steel: Vickers, Brinell, Knoop, and approximate tensile strength
| HV | HB | HK | Tensile ≈ (MPa) |
|---|---|---|---|
| 100 | 100 | 112 | — |
| 150 | 150 | 164 | 481 |
| 200 | 200 | 216 | 644 |
| 250 | 239 | 263 | 809 |
| 300 | 284 | 309 | 973 |
| 350 | 332 | 356 | 1147 |
| 400 | 379 | 412 | 1318 |
| 450 | 425 | 471 | 1496 |
| 500 | 471 | 528 | 1690 |
| 550 | 517 | 583 | 1893 |
| 600 | 565 | 636 | 2100 |
| 650 | 612 | 687 | 2250 |
| 700 | 656 * | 735 | 2400 |
| 750 | 691 * | 780 | — |
| 800 | 722 * | 822 | — |
| 850 | — | 859 | — |
| 900 | — | 895 | — |
| 940 | — | 920 | — |
Durometer overlap: Shore A to Shore D
Approximate selection guide for elastomers and plastics. Below Shore A 30 the D scale no longer reads; above about Shore D 58 the A scale tops out.
| Shore A | Shore D |
|---|---|
| 100 | 58 |
| 95 | 46 |
| 90 | 39 |
| 85 | 33 |
| 80 | 29 |
| 75 | 25 |
| 70 | 22 |
| 65 | 19 |
| 60 | 16 |
| 55 | 14 |
| 50 | 12 |
| 45 | 10 |
| 40 | 8 |
| 35 | 7 |
| 30 | 6 |
Mohs minerals and approximate Vickers equivalents
Very approximate: Mohs is an ordinal scratch scale, not an indentation scale.
| Mohs | Mineral | ≈ HV |
|---|---|---|
| 1 | Talc | 27 |
| 2 | Gypsum | 61 |
| 3 | Calcite | 157 |
| 4 | Fluorite | 315 |
| 5 | Apatite | 535 |
| 6 | Orthoclase feldspar | 817 |
| 7 | Quartz | 1161 |
| 8 | Topaz | 1567 |
| 9 | Corundum | 2035 |
| 10 | Diamond | 10000 |
Typical hardness of common materials
Typical values for material selection and machining references, not conversions.
| Material | Typical hardness | Notes |
|---|---|---|
| Rubber band | Shore A 25 | elastomer |
| Pencil eraser | Shore A 40 | elastomer |
| Car tyre tread | Shore A 60–70 | elastomer |
| O-ring (typical) | Shore A 70 | elastomer |
| Shopping-cart wheel | Shore A 95 | hard elastomer |
| Hard hat / polypropylene | Shore D 70–80 | rigid plastic |
| Acrylic (PMMA) | Shore D 85–90 | rigid plastic |
| Annealed mild steel | 120 HB | machinable |
| 6061-T6 aluminium | 95 HB | structural alloy |
| Annealed 304 stainless | 150 HV | austenitic, conversions N/A |
| Through-hardened tool steel | 700–830 HV | fully hardened |
| Case-hardened steel surface | 650–750 HV | surface only |
| Glass | Mohs 5.5 | brittle |
| Hardened steel | Mohs 8 | reference point |
| Tungsten carbide | Mohs 9 | cutting tools |
| Quartz | Mohs 7 (≈ 1160 HV) | abrasive mineral |
Frequently asked questions
What does this hardness conversion calculator do?
It converts a hardness number between six non-Rockwell scales: Vickers (HV), Brinell (HB), Knoop (HK), Shore A, Shore D, and Mohs. Steel-scale conversions use piecewise-linear interpolation of published ASTM E140 data points for non-austenitic steels; Shore A and Shore D convert through a published durometer overlap chart; Mohs converts through approximate mineral equivalents. For Rockwell C, B, and A conversions, use our Rockwell Hardness Converter instead.
How do I convert Brinell to Vickers?
Enter the Brinell value and select Brinell (HB) as the input scale; the calculator routes it through the Vickers hub using the empirical steel table. For example, 300 HB converts to approximately 317 HV. The result is an approximation, never a substitute for a direct Vickers measurement.
How do I convert Vickers to Knoop?
Select Vickers (HV) as the input scale. For example, 500 HV converts to approximately 528 HK for non-austenitic steels. Knoop numbers run slightly above Vickers numbers through most of the steel range because the two indenters sample the material differently.
What is the Brinell hardness formula?
Brinell hardness is defined as HB = 2F / (pi x D x (D - sqrt(D^2 - d^2))), where F is the test force in kilogram-force, D is the ball diameter in millimetres, and d is the measured indentation diameter in millimetres. For example, a 3000 kgf load with a 10 mm ball and a 4.00 mm impression gives approximately 229 HB. Use the Brinell calculator above to run the formula with your own numbers.
Can Shore hardness be converted to Vickers?
No. There is no published empirical conversion between Shore durometer and Vickers hardness because they are different test families: Shore measures the penetration of a spring-loaded indenter into elastomers and plastics, while Vickers measures a diamond indentation in metals. This tool converts Shore A to Shore D through their published overlap range (for example, Shore A 95 is approximately Shore D 46) and reports other scales as not convertible.
How do I convert Mohs hardness to Vickers?
Mohs is an ordinal scratch scale, so any conversion is very approximate. This tool uses published mineral equivalents: for example, quartz at Mohs 7 corresponds to approximately 1160 HV, and an 800 HV steel corresponds to approximately Mohs 5.9. Treat the result as a rough comparison, not a measurement.
How accurate are hardness scale conversions?
Every cross-scale conversion is an approximation. ASTM E140 states that converting from one hardness scale to another is only an approximate process, because each test samples a different combination of material properties. Converted values are valid for the materials the tables were built from (here, non-austenitic steels) and should never be reported as if they were directly measured.
What is the difference between HBW and HBS?
HBW uses a tungsten carbide ball and is the current standard designation under ISO 6506; HBS used a hardened steel ball and was withdrawn because the steel ball deforms on hard materials. Modern conversion tables, including the ones used here, are based on HBW with a 10 mm carbide ball and a 3000 kgf load.
Engineering disclaimer
All cross-scale conversions on this page are empirical approximations, not measurements. The steel table is interpolated from published ASTM E140 data for non-austenitic steels and does not apply to austenitic stainless steels, cast irons, or non-ferrous alloys. Shore durometer has no empirical conversion to metal hardness scales. Mohs equivalents are very rough. Tensile strength estimates apply to carbon and low-alloy steels only. Always report the scale you actually measured, and verify critical values with a calibrated test.
Table basis: ASTM E140 steel triplets (via the verified curation in our Rockwell converter), ASTM E92 Vickers/Knoop definitions, ISO 6506 Brinell definition, published durometer overlap charts (Ellsworth Adhesives / Kodiak Rubber), published Mohs mineral equivalents, and a steel tensile reference. No Rockwell conversion data is duplicated here; Rockwell conversions live in our Rockwell Hardness Converter.
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