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Hardness Conversion Calculator

Convert superficial Rockwell readings to Rockwell B or C — the scales most specifications call for.

How to use it

15T / 30T convert to Rockwell B (HRB), used for annealed material.
15N / 30N convert to Rockwell C (HRC), used for tempered material.
Choose 300 Series Stainless for 301, 302 / 304, 304L, 305, 316 / 316L and 321. Choose Non-Austenitic Steel for 410, 430, 17-7PH® and 1008 / 1010 low carbon steel.
Each scale has a valid range, shown under the Reading box. Readings outside it can't be converted.

Hardness tests are approximations. Conversions from one scale to another using ASTM E140 are inherently inaccurate. For precision-rolled thin-gauge stainless and steel products, hardness should be considered informational only. Questions? Ask us or call (800) 992-5015.

Reference tables

Choose a material and a table. When you use the calculator above, the matching table opens with your result highlighted.

Material

Table

Rockwell B — 300 Series Stainless (Austenitic)

Rockwell B (HRB)	15T	30T
100	91.5	80.4
99	91.2	79.7
98	90.8	79.0
97	90.4	78.3
96	90.1	77.7
95	89.7	77.0
94	89.3	76.3
93	88.9	75.6
92	88.6	74.9
91	88.2	74.2
90	87.8	73.5
89	87.5	72.8
88	87.1	72.1
87	86.7	71.4
86	86.4	70.7
85	86.0	70.0
84	85.6	69.3
83	85.2	68.6
82	84.9	67.9
81	84.5	67.2
80	84.1	66.5
79	83.8	65.8
78	83.4	65.1
77	83.0	64.4
76	82.6	63.7
75	82.3	63.0
74	81.9	62.4
73	81.5	61.7
72	81.2	61.0
71	80.8	60.3
70	80.4	59.6
69	80.1	58.9
68	79.7	58.2
67	79.3	57.5
66	78.9	56.8
65	78.6	56.1
64	78.2	55.4
63	77.8	54.7
62	77.5	54.0
61	77.1	53.3
60	76.7	52.6

Rockwell B — Non-Austenitic Steel (410, 430, 17-7PH®, 1008 / 1010)

Rockwell B (HRB)	15T	30T
100	93.1	83.1
99	92.8	82.5
98	92.5	81.8
97	92.1	81.1
96	91.8	80.4
95	91.5	79.8
94	91.2	79.1
93	90.8	78.4
92	90.5	77.8
91	90.2	77.1
90	89.9	76.4
89	89.5	75.8
88	89.2	75.1
87	88.9	74.4
86	88.6	73.8
85	88.2	73.1
84	87.9	72.4
83	87.6	71.8
82	87.3	71.1
81	86.9	70.4
80	86.6	69.7
79	86.3	69.1
78	86.0	68.4
77	85.6	67.7
76	85.3	67.1
75	85.0	66.4
74	84.7	65.7
73	84.3	65.1
72	84.0	64.4
71	83.7	63.7
70	83.4	63.1
69	83.0	62.4
68	82.7	61.7
67	82.4	61.0
66	82.1	60.4
65	81.8	59.7
64	81.4	59.0
63	81.1	58.4
62	80.8	57.7
61	80.5	57.0
60	80.1	56.4

Rockwell C — 300 Series Stainless (Austenitic)

Rockwell C (HRC)	15N	30N
48	84.1	66.2
47	83.6	65.3
46	83.1	64.5
45	82.6	63.6
44	82.1	62.7
43	81.6	61.8
42	81.0	61.0
41	80.5	60.1
40	80.0	59.2
39	79.5	58.4
38	79.0	57.5
37	78.5	56.6
36	78.0	55.7
35	77.5	54.9
34	77.0	54.0
33	76.5	53.1
32	75.9	52.3
31	75.4	51.4
30	74.9	50.5
29	74.4	49.6
28	73.9	48.8
27	73.4	47.9
26	72.9	47.0
25	72.4	46.2
24	71.9	45.3
23	71.3	44.4
22	70.8	43.5
21	70.3	42.7
20	69.8	41.8

Rockwell C — Non-Austenitic Steel (410, 430, 17-7PH®, 1008 / 1010)

Rockwell C (HRC)	15N	30N
60	90.2	77.5
59	89.8	76.6
58	89.3	75.7
57	88.9	74.8
56	88.3	73.9
55	87.9	73.0
54	87.4	72.0
53	86.9	71.2
52	86.4	70.2
51	85.9	69.4
50	85.5	68.5
49	85.0	67.6
48	84.5	66.7
47	83.9	65.8
46	83.5	64.8
45	83.0	64.0
44	82.5	63.1
43	82.0	62.2
42	81.5	61.3
41	80.9	60.4
40	80.4	59.5
39	79.9	58.6
38	79.4	57.7
37	78.8	56.8
36	78.3	55.9
35	77.7	55.0
34	77.2	54.2
33	76.6	53.3
32	76.1	52.1

Vickers / Knoop → Rockwell B — 300 Series Stainless

Rockwell B (HRB)	Vickers	Knoop	15T
100	–	–	91.5
99	–	–	91.2
98	–	–	90.8
97	241	258	90.4
96	236	253	90.1
95	233	246	89.7
94	229	240	89.3
93	213	231	88.9
92	207	225	88.6
91	194	220	88.2
90	188	214	87.8
89	185	210	87.5
88	180	205	87.1
87	175	199	86.7
86	173	196	86.4
85	169	190	86.0
84	165	187	85.6
83	162	182	85.2
82	159	178	84.9
81	156	174	84.5
80	153	171	84.1

Vickers / Knoop → Rockwell C — 300 Series Stainless

Rockwell C (HRC)	Vickers	Knoop	15N
48	479	504	84.1
47	459	482	83.6
46	447	469	83.1
45	435	457	82.6
44	424	445	82.1
43	413	433	81.6
42	403	421	81.0
41	393	409	80.5
40	384	398	80.0
39	374	388	79.5
38	369	379	79.0
37	358	–	78.5
36	–	–	78.0
35	337	355	77.5
34	328	348	77.0
33	325	340	76.5
32	316	330	75.9
31	308	321	75.4
30	300	314	74.9
29	293	306	74.4
28	286	300	73.9
27	280	294	73.4
26	275	287	72.9
25	267	281	72.4
24	261	275	71.9
23	257	268	71.3
22	251	–	70.8
21	–	–	70.3
20	–	–	69.8

– = no value listed for that hardness. Values per ASTM E140.