Hardness Scale Conversion Chart

Printable reference chart converting between Rockwell (HRC, HRB, HRA), Brinell (HB), Vickers (HV), and Knoop (HK), based on ASTM E140-12b for non-austenitic steels.

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Hardness Scale Conversion Chart

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HRC	HRB	HB	HV	HK	HRA
20	98	226	240	251	60.2
25	—	253	266	277	62.8
30	—	286	302	313	65.3
35	—	327	345	357	67.9
40	—	371	392	401	70.4
45	—	428	451	459	72.9
50	—	481	513	528	75.4
55	—	560	595	612	78
60	—	654	697	723	80.6
65	—	—	832	866	83.3
68	—	—	940	972	85

Soft-material range (Rockwell B)

Below ~20 HRC the Rockwell C indenter is unreliable. Use HRB or Brinell on annealed steels, brass, and aluminum alloys instead.

HRB	HRC	HB	HV	HK	HRA
60	—	106	105	109	—
65	—	114	114	116	—
70	—	121	124	124	—
75	—	130	134	132	—
80	—	141	144	142	—
85	—	154	156	151	—
90	—	172	175	168	—
95	—	196	199	192	—
100	—	240	240	251	—

Notes

• HRC: Rockwell C — diamond cone, 150 kgf. For hardened steels (~20–70 HRC).
• HRB: Rockwell B — 1/16" tungsten carbide ball, 100 kgf. For soft to medium materials.
• HB (HBW): Brinell — 10 mm WC ball, 3000 kgf. Loses accuracy above ~55 HRC; the ball deforms.
• HV: Vickers — square-base diamond pyramid. Universal scale across all hardness ranges.
• HK: Knoop — rhombic diamond pyramid. Best for thin layers, coatings, and case-depth profiles.
• HRA: Rockwell A — diamond cone, 60 kgf. For very hard materials (carbides, cermets).
• Conversions follow ASTM E140-12b for non-austenitic carbon and alloy steels. Austenitic stainless, copper, aluminum, and titanium alloys have different curves — use scale-specific tables.
• Conversions are approximate; published agreement is typically ±1 HRC. Direct measurement on the scale called out in the spec is always preferred.

HRB	HRC	HB	HV	HK	HRA
60	—	106	105	109	—
65	—	114	114	116	—
70	—	121	124	124	—
75	—	130	134	132	—
80	—	141	144	142	—
85	—	154	156	151	—
90	—	172	175	168	—
95	—	196	199	192	—
100	—	240	240	251	—

HRB	HRC	HB	HV	HK	HRA
60	—	106	105	109	—
65	—	114	114	116	—
70	—	121	124	124	—
75	—	130	134	132	—
80	—	141	144	142	—
85	—	154	156	151	—
90	—	172	175	168	—
95	—	196	199	192	—
100	—	240	240	251	—

HRB	HRC	HB	HV	HK	HRA
60	—	106	105	109	—
65	—	114	114	116	—
70	—	121	124	124	—
75	—	130	134	132	—
80	—	141	144	142	—
85	—	154	156	151	—
90	—	172	175	168	—
95	—	196	199	192	—
100	—	240	240	251	—