Engineering · Reference

Hardness conversion chart.

Rockwell C, Rockwell B, Vickers, Brinell, and approximate tensile strength — converted from Mitutoyo's approximate reference for steel. Use this when a drawing calls out hardness in one scale and your inspection equipment reads another, or when you need to estimate ultimate tensile from a hardness reading.

Scales covered

Standard

ASTM E140

Material

Steel

Range

50 HRB → 68 HRC

Print current reference table Mitutoyo source chart (2017)

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Hardness Scale Comparator

Approximate steel-reference comparisons, not inspection acceptance or alloy identification. Rows are transcribed from Mitutoyo Bulletin 2059(2). HRB-region Vickers values are withheld: the source has a separate Knoop column and a combined HB/HV heading, not a separately identified Vickers test column. A dash means unavailable here, not zero.

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Snaps to the nearest available source row, not an interpolated result.

Rockwell C (HRC)

Diamond Cone / 150 kgf

Rockwell B (HRB)

—

1/16" Ball / 100 kgf

Vickers (HV)

318

Diamond Pyramid / Var. load

Brinell (HB)

301

10 mm Ball / 3000 kgf

Estimated Tensile Strength (UTS)

146 ksi 1007 MPa

*Approximate correlation from Mitutoyo's approximate reference. Valid for carbon & alloy steels only.

Indenter Micro-Mechanics

Physical Test Geometry

Rockwell C Cone

Rockwell Brale Indenter: Ground diamond cone with a 120° tip angle and a 0.2 mm spherical radius. The minor load establishes reference depth, and the major load measures the delta indentation depth.

Mechanical Implications

Approximate UTS & Alloy Compatibility

Machining & Cutting Advisory

Pre-hardened State (32 HRC): Readily machinable with standard carbide tooling. Chips break cleanly. Suitable for highly complex custom shafts and tooling fixtures where post-machining heat treatment distortion must be fully avoided.

Data Reference

Master Conversion Table

Index	Rockwell C (HRC)	Rockwell B (HRB)	Vickers (HV)	Brinell (HB)	UTS (ksi)	UTS (MPa)
#1	68	—	940	—	—	—
#2	65	—	832	739	—	—
#3	62	—	746	688	—	—
#4	60	—	697	654	—	—
#5	58	—	653	615	338	2330
#6	56	—	613	577	313	2158
#7	54	—	577	543	292	2013
#8	52	—	544	512	273	1882
#9	50	—	513	481	255	1758
#10	48	—	484	455	238	1641
#11	46	—	458	432	221	1524
#12	44	—	434	409	208	1434
#13	42	—	412	390	194	1338
#14	40	—	392	371	182	1255
#15	38	—	372	353	171	1179
#16	36	—	354	336	161	1110
#17	34	—	336	319	152	1048
#18	32	—	318	301	146	1007
#19	30	—	302	286	138	951
#20	28	—	286	271	131	903
#21	26	—	272	258	125	862
#22	24	—	260	247	119	820
#23	22	—	248	237	115	793
#24	20	—	238	226	110	758
#25	—	98	0	228	109	752
#26	—	95	0	210	100	689
#27	—	92	0	195	92	634
#28	—	90	0	185	89	614
#29	—	86	0	169	83	572
#30	—	80	0	150	72	496
#31	—	75	0	137	66	455
#32	—	70	0	125	61	421
#33	—	60	0	107	—	—
#34	—	50	0	—	—	—

How to use this

Scale selection & caveats.

HRC for hardened steel ≥ 20 HRC.

Diamond cone, 150 kgf load. Standard for tool steel, hardened 4140/4340, hardened 17-4PH (H900–H1075). Below 20 HRC the readings get unreliable.
HRB for soft-to-medium steel and some non-ferrous.

1/16″ ball, 100 kgf load. Use for annealed steel, brass, aluminum bronze, hard plastics. Above ~100 HRB switch to HRC.
HV (Vickers) for everything.

Diamond pyramid, variable load. Single scale that covers soft aluminum to carbide. Common for thin coatings, hardened-case-depth measurement, and material-research work.
HB (Brinell) for thicker work and castings.

10 mm ball, 3000 kgf for steel. Large indent gives good average for non-uniform material. Common on cast-iron specs, large forgings. The HB column here is the source’s 3000 kgf / 10 mm ball column; no carbide-ball test equivalence is implied.
Tensile strength is approximate.

The UTS values are the approximate steel correlations published in Mitutoyo Bulletin 2059(2), not independently measured strengths or design allowables. A dash means that this source does not supply a value. Do not infer alloy identity or acceptance from a converted reading.
Non-steel conversions are not transferable.

The values above are for steel. For aluminum, copper, titanium, and other non-ferrous, use material-specific conversion tables (often in the alloy datasheet) or measure on multiple scales directly.