Is Rockwell C the same as Vickers divided by 10?

It is a rough approximation in the mid range, not a definition. For example 45 HRC corresponds to about 446 HV, and 446 ÷ 10 = 44.6. The relationship drifts at both ends of the range — use the table or the ASTM E140 conversion values for anything that matters.

How do I convert Brinell to tensile strength?

For steel, tensile strength in psi is approximately Brinell × 515 for Brinell values up to 175, and Brinell × 490 above 175. This is the ASTM E140 relation. It is an estimate — the scatter is roughly ±10% for most steels.

Why can't I convert hardness scales exactly?

Because each test measures a different geometric response to indentation — Rockwell measures depth, Brinell measures impression diameter, Vickers measures diagonal length. A conversion table is an empirical fit through paired measurements on a specific material class, not a physical relationship between the scales.

Which hardness scale should I specify on a drawing?

Specify the scale you can actually test for, and one matched to the hardness range. Use Rockwell C for hardened steel (20–70 HRC), Rockwell B for soft metals, Brinell for castings, and Vickers for thin or case-hardened sections. Do not specify a scale and then accept a converted value from a different scale.

What is 20 HRC in Brinell?

20 HRC converts to approximately 238 HB on the ASTM E140 steel table. Below about 20 HRC, Rockwell C becomes unreliable and the Brinell or Rockwell B scale is preferred.

Does hardness conversion work for aluminium and copper alloys?

No. The table above is for steel only. Aluminium, copper and their alloys each have separate conversion tables because they work-harden and respond to indentation differently. Using steel conversions on aluminium gives large errors.

Hardness Conversion Chart

Convert Rockwell C, Rockwell B, Rockwell A, Brinell and Vickers hardness values for steel — with approximate equivalent tensile strength and the formulas behind the conversions.

Page last changed 2026-10-19 · based on ASTM E140-12b

Quick Answer

Hardness scales are not interchangeable by a single formula — conversions are empirical, established by testing the same material on each scale. The table below gives the ASTM E140 conversion values for steel. As a rough guide, Rockwell C ≈ Vickers ÷ 10, and Brinell ≈ Vickers ÷ 1.05 in the mid range.

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Rockwell / Brinell / Vickers Conversion Table (Steel)

Rockwell C 150 kg^[1]	Rockwell B 100 kg^[1]	Rockwell A 60 kg^[1]	Brinell 3000 kg^[1]	Vickers HV^[1]	Approx. tensile psi^[2]
70 #	—	86.5	—	1076	—
69 #	—	86	—	1044	—
68 #	—	85.6	—	940	—
67 #	—	85	—	900	—
66 #	—	84.5	—	865	—
65 #	—	83.9	739	832	362,110
64 #	—	83.4	722	800	353,780
63 #	—	82.8	705	772	345,450
62 #	—	82.3	688	746	337,120
61 #	—	81.8	670	720	328,300
60 #	—	81.2	654	697	320,460
59 #	—	80.7	634	674	310,660
58 #	—	80.1	615	653	301,350
57 #	—	79.6	595	633	291,550
56 #	—	79	577	613	282,730
55 #	120	78.5	560	595	274,400
54 #	120	78	543	577	266,070
53 #	119	77.4	525	560	257,250
52 #	119	76.8	500	544	245,000
51 #	118	76.3	487	528	238,630
50 #	117	75.9	475	513	232,750
49 #	117	75.2	464	498	227,360
48 #	116	74.7	451	484	220,990
47 #	116	74.1	442	471	216,580
46 #	115	73.6	432	458	211,680
45 #	115	73.1	421	446	206,290
44 #	114	72.5	409	434	200,410
43 #	113	72	400	423	196,000
42 #	113	71.5	390	412	191,100
41 #	112	70.9	381	402	186,690
40 #	112	70.4	371	392	181,790
39 #	111	69.9	362	382	177,380
38 #	110	69.4	353	372	172,970
37 #	110	68.9	344	363	168,560
36 #	109	68.4	336	354	164,640
35 #	109	67.9	327	345	160,230
34 #	108	67.4	319	336	156,310
33 #	108	66.8	311	327	152,390
32 #	107	66.3	301	318	147,490
31 #	106	65.8	294	310	144,060
30 #	105	65.3	286	302	140,140
29 #	104	64.7	279	294	136,710
28 #	104	64.3	271	286	132,790
27 #	103	63.8	264	279	129,360
26 #	103	63.3	258	272	126,420
25 #	102	62.8	253	266	123,970
24 #	101	62.4	247	260	121,030
23 #	100	62	240	254	117,600
22 #	99	61.5	234	248	114,660
21 #	98	61	228	243	111,720
20 #	97	60.5	222	238	108,780
18 #	96	59	216	230	105,840
16 #	95	58	210	222	102,900
15 #	94	57.5	205	213	100,450
13 #	93	57	200	208	98,000
12 #	92	56.5	195	204	95,550
10 #	91	56	190	196	93,100
9 #	90	55.5	185	192	90,650
8 #	89	55	180	188	88,200
7 #	88	54	176	184	86,240
6 #	87	53.5	172	180	88,580
5 #	86	53	169	176	87,035
4 #	85	52.5	165	173	84,975
3 #	84	52	162	170	83,430
2 #	83	51	159	166	81,885
1 #	82	50.5	156	163	80,340
0 #	81	50	153	160	78,795

Conversion values follow ASTM E140 for steel. Conversions between hardness scales are empirical — they are only valid for the material class they were established on, and are approximate. Tensile strength is estimated from Brinell using the ASTM E140 relation (HB × 515 below HB 175, HB × 490 above). Do not use converted values for acceptance testing; specify the required scale directly on the drawing.

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Why Hardness Conversions Are Approximate

Each hardness test measures something different. Rockwell measures the depth of penetration by a specified indenter under a specified load. Brinell measures the diameter of a spherical impression. Vickers measures the diagonal of a pyramidal impression. Because the indentation geometries differ, the scales respond differently to the same material — a conversion table is a fitted curve through paired test results, not a physical law.

The practical consequences:

Conversions are material-class specific. The table above is for steel. Cast iron, aluminium and copper alloys each have their own conversion tables.
Conversions degrade at the extremes. Below about 20 HRC or above 65 HRC, agreement between scales falls off sharply.
Converted values are for guidance only. For acceptance testing, specify the required scale and test method on the drawing rather than a converted equivalent.

The Conversion Formulas

For rough work in the mid range the following approximations are useful — they are not substitutes for the table above.

Vickers ≈ 10 × Rockwell C
Brinell ≈ Vickers ÷ 1.05 (mid range)
Tensile (psi) ≈ Brinell × 515 (HB ≤ 175)
Tensile (psi) ≈ Brinell × 490 (HB > 175)

The last two are the ASTM E140 relations between Brinell hardness and tensile strength for steel. They work reasonably between roughly 200 and 400 HB; outside that range the scatter grows.

Choosing the Right Scale

Selection is driven by the hardness range and the part geometry:

Rockwell C (150 kg, diamond) — hardened and tempered steels, roughly 20–70 HRC. The default for heat-treated parts.
Rockwell B (100 kg, 1/16 in ball) — soft steels, brass, aluminium, roughly 20–100 HRB. Below 20 HRC the C scale becomes insensitive and B takes over.
Brinell (3000 kg, 10 mm ball) — coarse-grained and cast materials where a large impression averages out structure. Common for castings and forgings.
Vickers — one continuous scale from very soft to very hard, and usable on thin sections and case-hardened layers because the indenter is small.

Frequently Asked Questions

Is Rockwell C the same as Vickers divided by 10?: It is a rough approximation in the mid range, not a definition. For example 45 HRC corresponds to about 446 HV, and 446 ÷ 10 = 44.6. The relationship drifts at both ends of the range — use the table or the ASTM E140 conversion values for anything that matters.
How do I convert Brinell to tensile strength?: For steel, tensile strength in psi is approximately Brinell × 515 for Brinell values up to 175, and Brinell × 490 above 175. This is the ASTM E140 relation. It is an estimate — the scatter is roughly ±10% for most steels.
Why can't I convert hardness scales exactly?: Because each test measures a different geometric response to indentation — Rockwell measures depth, Brinell measures impression diameter, Vickers measures diagonal length. A conversion table is an empirical fit through paired measurements on a specific material class, not a physical relationship between the scales.
Which hardness scale should I specify on a drawing?: Specify the scale you can actually test for, and one matched to the hardness range. Use Rockwell C for hardened steel (20–70 HRC), Rockwell B for soft metals, Brinell for castings, and Vickers for thin or case-hardened sections. Do not specify a scale and then accept a converted value from a different scale.
What is 20 HRC in Brinell?: 20 HRC converts to approximately 238 HB on the ASTM E140 steel table. Below about 20 HRC, Rockwell C becomes unreliable and the Brinell or Rockwell B scale is preferred.
Does hardness conversion work for aluminium and copper alloys?: No. The table above is for steel only. Aluminium, copper and their alloys each have separate conversion tables because they work-harden and respond to indentation differently. Using steel conversions on aluminium gives large errors.

Value Sources

References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.

#	Source	Type	Revision / method
[1]	ASTM E140 — Standard Hardness Conversion Tables for Metals	reference	ASTM E140-12b — source
[2]	Tensile strength estimate	derived	ASTM E140 relation from Brinell: HB × 515 for HB ≤ 175, HB × 490 for HB > 175. Estimated value — scatter is roughly ±10% for most steels.

Data Sources

Standard	Revision	What it covers on this page
ASTM E140 — Standard Hardness Conversion Tables for Metals	ASTM E140-12b	conversion between Rockwell A/B/C, Brinell and Vickers for steel

Verification scope

No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.

Derived values — the following values on this page are calculated, not taken directly from the standard:

Value	How it is derived
Approx. tensile (psi)	ASTM E140 relation from Brinell: HB × 515 for HB ≤ 175, HB × 490 for HB > 175. Estimated — scatter is roughly ±10% for most steels.

Nominal values as published in the referenced standard. Manufacturing tolerances apply.

Accuracy and use. Use the source notes and recorded verification scope above to assess each value. Calculated values follow the stated derivations; compilation values may lack a confirmed original document or product condition. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Read the source notes, calculation methods and verification scope above before reusing a value. To cite this page:

Plain text

Engineering Reference. "Hardness Conversion Chart." https://refmanual.com/charts/hardness-conversion/ (accessed 2026-10-19). Data from ASTM E140 — Standard Hardness Conversion Tables for Metals, ASTM E140-12b.

BibTeX

@misc{hardness-conversion,
  title        = {Hardness Conversion Chart},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/charts/hardness-conversion/}},
  note         = {Accessed: 2026-10-19},
  source       = {ASTM E140 — Standard Hardness Conversion Tables for Metals, ASTM E140-12b}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - Hardness Conversion Chart
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/charts/hardness-conversion/
PY  - 2026
DA  - 2026-10-19
N1  - Source: ASTM E140 — Standard Hardness Conversion Tables for Metals, ASTM E140-12b
ER  -

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