Approximate Rockwell Hardness Conversion Chart

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Rockwell Hardness Number Rockwell Superficial Hardness Number
C Scale,
150-kgf Diamond Penetrator (HRC)
A Scale,
60-kgf
Diamond Penetrator (HRA)
15-N Scale,
15 kgf Superficial Diamond Penetrator (HR 15-N)
30-N Scale, 30-kgf Superficial Diamond Penetrator (HR 30-N) 45-N Scale, 45-kgf Superficial Diamond Penetrator (HR 45-N)
48.00 74.40 84.10 66.20 52.10
47.00 73.90 83.60 65.30 50.90
46.00 73.40 83.10 64.50 49.80
45.00 72.90 82.60 63.60 48.70
44.00 72.40 82.10 62.70 47.50
43.00 71.90 81.60 61.80 46.40
42.00 71.40 81.00 61.00 45.20
41.00 70.90 80.50 60.10 44.10
40.00 70.40 80.00 59.20 43.00
39.00 69.90 79.50 58.40 41.80
38.00 69.30 79.00 57.50 40.70
37.00 68.80 78.50 56.60 39.60
36.00 68.30 78.00 55.70 38.40
35.00 67.80 77.50 54.90 37.30
34.00 67.30 77.00 54.00 36.10
33.00 66.80 76.50 53.10 35.00
32.00 66.30 75.90 52.30 33.90
31.00 65.80 75.40 51.40 32.70
30.00 65.30 74.90 50.50 31.60
29.00 64.80 74.40 49.60 30.40
28.00 64.30 73.90 48.80 29.30
27.00 63.80 73.40 47.90 28.20
26.00 63.30 72.90 47.00 27.00
25.00 62.80 72.40 46.20 25.90
24.00 62.30 71.90 45.30 24.80
23.00 61.80 71.30 44.40 23.60
22.00 61.30 70.80 43.50 22.50
21.00 60.80 70.30 42.70 21.30
20.00 60.30 69.80 41.80 20.20
Rockwell Hardness Number Rockwell Superficial Hardness Number
B Scale,
100-kgf
1/16 in (1.588mm) ball
(HRB)
A Scale,
60-kgf
Diamond Penetrator
(HRA)
15-T Scale, 15 kgf
1/16 in (1.588 mm) ball
(HR 15-T)
30-T Scale, 30-kgf
1/16 in (1.588mm) ball
(HR 30-T)
45-T Scale, 45-kgf
1/16 in (1.588mm) ball
(HR 45-T)
100 61.5 91.5 80.4 70.2
99 60.9 91.2 79.7 69.2
98 60.3 90.8 79.0 68.2
97 59.7 90.4 78.3 67.2
96 59.1 90.1 77.7 66.1
95 58.5 89.7 77.0 65.1
94 58.0 89.3 76.3 64.1
93 57.4 88.9 75.6 62.1
92 56.8 88.6 74.9 62.1
91 56.2 88.2 74.2 61.1
90 55.6 87.8 73.5 60.1
89 55.0 87.5 72.8 59.0
88 54.5 87.1 72.1 58.0
87 53.9 86.7 71.4 57.0
86 53.3 86.4 70.7 56.0
85 52.7 86.0 70.0 55.0
84 52.1 85.6 69.3 54.0
83 51.5 85.2 68.6 52.9
82 50.9 84.9 67.9 51.9
81 50.4 84.5 67.2 50.9
80 49.8 84.1 66.5 49.9
79 49.2 83.8 65.8 48.9
78 48.6 83.4 65.1 47.9
77 48.0 83.0 64.4 46.8
76 47.4 82.6 63.7 45.8
75 46.9 82.3 63.0 44.8
74 46.3 81.9 62.4 43.8
73 45.7 81.5 61.7 42.6
72 45.1 81.2 61.0 41.8
71 44.5 80.8 60.3 40.7
70 43.9 80.4 59.6 39.7
69 43.3 80.1 58.9 38.7
68 42.8 79.7 58.2 37.7
67 42.2 79.3 57.5 36.7
66 41.6 78.9 56.8 35.7
65 41.0 78.6 56.1 34.7
64 40.4 78.2 55.4 33.6
63 39.8 77.8 54.7 32.6
62 39.3 77.5 54.0 31.6
61 38.7 77.1 53.3 30.6
60 38.1 76.7 52.6 29.6