Hardness Conversion Calculator
Convert a hardness reading between the Brinell, Rockwell, Vickers, and Shore scales — for steel and common nonferrous alloys, per Machinery’s Handbook 29.
Calculator
Formulas
Have a raw Brinell test reading (test load, ball diameter, and measured indentation diameter) instead of a hardness number? Use our Brinell hardness calculator to compute HBW from MH29 p. 505, then return here to convert that Brinell number to Rockwell, Vickers, or Shore.
Hardness to Tensile Strength Conversion
TS (psi) = BHN × 515 (for BHN ≤ 175)
TS (psi) = BHN × 490 (for BHN > 175)
TS = approximate tensile strength of steel [force / area] — psi (formula as-given)
BHN = Brinell hardness number [dimensionless]
Machinery’s Handbook 29th Ed., p. 509. For steels only — does not apply to nonferrous metals except certain aluminum alloys. The linear approximation is most reliable for medium-hardness steel; the calculator suppresses the tensile estimate above BHN 500 because MH29 prints standard-ball entries in that range in parentheses (out of normal range) and the linear relation is anchored on the standard-ball Brinell test.
Hardness Conversion Chart
This Brinell hardness conversion chart cross-references Brinell (HB / BHN), Rockwell C (HRC) and Rockwell B (HRB), Vickers (HV), Shore Scleroscope (HSc), and the Rockwell A and Rockwell Superficial scales. Engineers reference these tables when a hardness specification is written in one scale and inspection results are read in another — for example, a drawing calling out HRC and a shop with only a Brinell tester.
Brinell to Rockwell C conversion (hardened steel, MH29 Table 1): HB 226 = HRC 20, HB 286 = HRC 30, HB 371 = HRC 40, HB 442 = HRC 47. Above HB 442 the standard steel ball is past its valid range — use the tungsten carbide ball or convert via Vickers (see HRC–HV column in the table).
Choose the material condition below to switch between MH29 Table 1 (hardened steel) and Table 2 (soft steel, cast iron, and nonferrous — with the material-family exclusions on MH29 p. 511).
( ) = beyond the normal indenter range per MH29 p. 509 footnote, given for information only. Knoop, Leeb, and Shore A/D durometer are not part of MH29 Tables 1 or 2 and are not supported by this chart; see ASTM E140 for Knoop conversions.
Source: Machinery’s Handbook 29th Ed. — Brinell test description and BHN formula: p. 505; hardened steel comparative table (Table 1): pp. 508–509; soft steel, cast iron, and nonferrous comparative table (Table 2): pp. 510–511. Values shown in parentheses are beyond the normal range of the indenter (per MH29 p. 509 footnote: “Values in ( ) are beyond the normal range and are given for information only.”). Table 2 is explicitly not applicable to annealed metals of high B-scale hardness (austenitic stainless, nickel and high-nickel alloys) nor to cold-worked metals of low B-scale hardness (aluminum and the softer alloys), per the MH29 p. 511 footnote. Tensile-strength estimate (steels only): MH29 p. 509.
A hardness conversion is an approximate mapping between different hardness scales. Each scale (Brinell HB or BHN, Rockwell C and B (HRC, HRB), Vickers HV, Shore Scleroscope HSc, and the Rockwell superficial scales) uses a different indenter shape, load, and dwell time, so conversions are reference-only. Machinery’s Handbook 29 Tables 1 and 2 specify the standard equivalences for steel; the MH29 Table 1 boldface values correspond to ASTM E140-67.
Engineers also call this lookup a hardness conversion table. The same chart is sometimes called a hardness equivalence table. On older drawings it may be labeled an HRC-to-BHN conversion. The hardness conversion calculator above reports every scale at once.
How to Use This Hardness Converter
Pick the scale of your input reading from the dropdown, type the value, and the calculator reports every equivalent on the applicable MH29 table. For hardened steel (HRC 20 and above, or HB 226 and above), use Table 1. For unhardened steel, soft-temper steel, cast iron, and most copper-base nonferrous alloys, use Table 2 — with the explicit exclusions on MH29 p. 511: Table 2 does not apply to annealed austenitic stainless steels, nickel and high-nickel alloys, or cold-worked aluminum and the softer alloys. If you have a raw test reading (load, ball diameter, and measured indent diameter) instead of a hardness number, use our Brinell hardness calculator first, then return here to convert the result. To save a printable hardness conversion chart, click Print / PDF below the table.
Engineers writing drawing callouts typically specify a single hardness scale (most commonly HRC for hardened steel or HRB for softer materials) with a range like “28–32 HRC.” Conversions on this page are approximations based on ASTM E140-67 and should not be substituted for direct measurement on the specified scale. To estimate part weight once you have matched material and hardness, see our density of metals chart.
Example: Verifying a 4140 Shaft Heat-Treated to HRC 32
A drawing calls for AISI 4140 prehard shaft to 28–32 HRC. The receiving inspector has a Brinell tester, not a Rockwell C tester. Looking up HRC 32 in Table 1 (MH29 pp. 508–509) gives HB 301 (standard ball, 3000 kgf); HRC 28 gives HB 271. The accepted Brinell range is therefore HB 271–301 (round to HB 270–305 for inspection practice). The approximate tensile strength from MH29 p. 509 is 271 × 490 = 133,000 psi at the low end and 301 × 490 = 147,000 psi at the high end.
Frequently Asked Questions
How do I convert Brinell hardness to Rockwell C?
For hardened steel, Brinell readings convert to Rockwell C approximately as follows from MH29 Table 1 (pp. 508–509, based on ASTM E140-67): HB 226 = HRC 20, HB 286 = HRC 30, HB 371 = HRC 40, HB 442 = HRC 47. Above HRC 47, MH29 prints standard-ball values in parentheses (for example, HB (475) at HRC 50), meaning the standard ball is past its valid range — switch to the tungsten carbide ball or convert via Vickers. Above HRC 52 the standard-ball column ends entirely; at HRC 60 the standard-ball cell is blank and MH29 lists a Hultgren-ball value (613) and a tungsten-carbide-ball value (654), both parenthesized as out of normal range per the MH29 p. 509 footnote. Enter your Brinell value in the calculator above and select 'Brinell (HB)' as the input scale to see every equivalent.
How do I convert HRC to BHN (Rockwell C to Brinell)?
To convert HRC to BHN, use the published MH29 Table 1 (3000 kgf, 10 mm ball, pp. 508–509): HRC 20 = HB 226, HRC 30 = HB 286, HRC 40 = HB 371, HRC 47 = HB 442 (the last in-range value for the standard steel ball). The standard-ball Brinell values stop being valid once they pass the 450 BHN limit for that ball (MH29 p. 505), so above HRC 47 MH29 prints them in parentheses (the first is (451) at HRC 48) — use the tungsten carbide ball or convert via Vickers. At HRC 60 the carbide-ball reading is (654), parenthesized as out of normal range. Per MH29 p. 505, a standard steel ball is used on material with a BHN not over 450, a Hultgren ball not over 500, and a carbide ball not over 630.
Are hardness conversions exact?
No. Hardness conversions are approximations because each scale measures resistance to indentation with a different indenter shape, load, and dwell time. The MH29 p. 509 footnote calls values printed in parentheses 'beyond the normal range and are given for information only.' MH29 p. 511 also limits Table 2 to specific material families and excludes annealed austenitic stainless, nickel and high-nickel alloys, and cold-worked aluminum and the softer alloys. For critical applications, measure on the scale the specification calls out rather than relying on a converted value.
What is the relationship between hardness and tensile strength?
For steels, Machinery's Handbook 29th Ed. (p. 509) gives two approximate relations: Tensile strength (psi) = BHN × 515 for Brinell numbers up to 175, and TS (psi) = BHN × 490 for Brinell numbers above 175. For example, BHN 200 corresponds to roughly 98,000 psi (676 MPa). MH29 explicitly notes this relationship does not apply to nonferrous metals except certain aluminum alloys. The calculator displays the estimated tensile strength alongside each conversion when the input scale and value correspond to a steel hardness range.
Related Calculators
- Stainless Steel Grades Chart — Yield, tensile, and typical hardness for common stainless grades
- Density of Metals Chart — Specific gravity and density for steel, aluminum, copper, brass, titanium
- Metal Weight Calculator — Calculate weight by shape and material for plate, bar, tube, and beam
References
- Oberg, E. et al. Machinery’s Handbook, 29th Edition, Industrial Press, 2012, p. 505. Brinell Hardness Test — algebraic BHN formula and BHN ranges for each standard test load. MH29 references ASTM E10-66 specifically; the current revision is ASTM E10.
- Oberg, E. et al. Machinery’s Handbook, 29th Edition, Table 1, pp. 508–509. Comparative Hardness Scales for Steel — Rockwell C/A/D, Vickers, Brinell (standard / Hultgren / tungsten carbide ball), Rockwell Superficial (15-N, 30-N, 45-N), Shore Scleroscope. Boldface values correspond to ASTM E140-67. Values in parentheses are beyond the normal range of the indenter per the MH29 p. 509 footnote.
- Oberg, E. et al. Machinery’s Handbook, 29th Edition, Table 2, pp. 510–511 (with parallel narrative on pp. 506–507). Comparative Hardness Scales for Unhardened Steel, Soft-Temper Steel, Grey and Malleable Cast Iron, and Nonferrous Alloys — Rockwell B/F/G/E/H/K/A, Rockwell 15-T/30-T/45-T, Brinell standard ball (500 kgf and 3000 kgf). Footnote on p. 511 excludes annealed austenitic stainless, nickel and high-nickel alloys, and cold-worked aluminum and softer alloys. Compiled by Wilson Mechanical Instrument Co.
- Oberg, E. et al. Machinery’s Handbook, 29th Edition, p. 509. Relation Between Hardness and Tensile Strength — for steels, TS (psi) = BHN × 515 (BHN ≤ 175) or BHN × 490 (BHN > 175).
- ASTM E140 — Standard Hardness Conversion Tables for Metals. Original reference standard cited in MH29 Table 1.
- SAE J417 — Hardness Tests and Hardness Number Conversions. Canonical automotive/manufacturing cross-reference for BHN-to-tensile relations.
Data last verified: June 2026
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