Bolt Torque Chart
Suggested Starting Values
The below estimated torque calculations are only offered as a guide. Use of its content by anyone is the sole responsibility of that person and they assume all risk. Due to many variables that affect the torque-tension relationship like human error, surface texture, and lubrication the only way to determine the correct torque is through experimentation under actual joint and assembly conditions.
ASTM A307
Bolt Size |
TPI |
Proof Load (lbs) |
Clamp Load (lbs) |
Tightening Torque (ft lbs) |
Waxed |
Galv |
Plain |
1/4 |
20 |
1145 |
859 |
2 |
4 |
4 |
5/16 |
18 |
1886 |
1415 |
4 |
9 |
7 |
3/8 |
16 |
2790 |
2093 |
7 |
16 |
13 |
7/16 |
14 |
3827 |
2870 |
10 |
26 |
21 |
1/2 |
13 |
5108 |
3831 |
16 |
40 |
32 |
9/16 |
12 |
6552 |
4914 |
23 |
58 |
46 |
5/8 |
11 |
8136 |
6102 |
32 |
79 |
64 |
3/4 |
10 |
12024 |
9018 |
56 |
141 |
113 |
7/8 |
9 |
15200 |
11400 |
83 |
208 |
166 |
1 |
8 |
20000 |
15000 |
125 |
313 |
250 |
1 1/8 |
7 |
25200 |
18900 |
177 |
443 |
354 |
1 1/4 |
7 |
32000 |
24000 |
250 |
625 |
500 |
1 3/8 |
6 |
38100 |
28575 |
327 |
819 |
655 |
1 1/2 |
6 |
46400 |
34800 |
435 |
1088 |
870 |
1 3/4 |
5 |
68400 |
51300 |
748 |
1870 |
1496 |
2 |
4 1/2 |
90000 |
67500 |
1125 |
2813 |
2250 |
2 1/4 |
4 1/2 |
117000 |
87750 |
1645 |
4113 |
3291 |
2 1/2 |
4 |
144000 |
108000 |
2250 |
5625 |
4500 |
2 3/4 |
4 |
177480 |
133110 |
3050 |
7626 |
6101 |
3 |
4 |
214920 |
161190 |
4030 |
10074 |
8060 |
3 1/4 |
4 |
255600 |
191700 |
5192 |
12980 |
10384 |
3 1/2 |
4 |
299880 |
224910 |
6560 |
16400 |
13120 |
3 3/4 |
4 |
347760 |
260820 |
8151 |
20377 |
16301 |
4 |
4 |
398880 |
299160 |
9972 |
24930 |
19944 |
SAE GRADE 2
Bolt Size |
TPI |
Proof Load (lbs) |
Clamp Load (lbs) |
Tightening Torque (ft lbs) |
Waxed |
Galv |
Plain |
1/4 |
20 |
1750 |
1313 |
3 |
7 |
5 |
5/16 |
18 |
2900 |
2175 |
6 |
14 |
11 |
3/8 |
16 |
4250 |
3188 |
10 |
25 |
20 |
7/16 |
14 |
5850 |
4388 |
16 |
40 |
32 |
1/2 |
13 |
7800 |
5850 |
24 |
61 |
49 |
9/16 |
12 |
10000 |
7500 |
35 |
88 |
70 |
5/8 |
11 |
12400 |
9300 |
48 |
121 |
97 |
3/4 |
10 |
18400 |
13800 |
86 |
216 |
173 |
7/8 |
9 |
15200 |
11400 |
83 |
208 |
166 |
1 |
8 |
20000 |
15000 |
125 |
313 |
250 |
1 1/8 |
7 |
25200 |
18900 |
177 |
443 |
354 |
1 1/4 |
7 |
32000 |
24000 |
250 |
625 |
500 |
1 3/8 |
6 |
38100 |
28575 |
327 |
819 |
655 |
1 1/2 |
6 |
46400 |
34800 |
435 |
1088 |
870 |
ASTM A325 / ASTM A449 / SAE GRADE 5
Bolt Size |
TPI |
Proof Load (lbs) |
Clamp Load (lbs) |
Tightening Torque (ft lbs) |
Waxed |
Galv |
Plain |
1/4 |
20 |
2700 |
2025 |
4 |
11 |
8 |
5/16 |
18 |
4450 |
3338 |
9 |
22 |
17 |
3/8 |
16 |
6600 |
4950 |
15 |
39 |
31 |
7/16 |
14 |
9050 |
6788 |
25 |
62 |
49 |
1/2 |
13 |
12050 |
9038 |
38 |
94 |
75 |
9/16 |
12 |
15450 |
11588 |
54 |
136 |
109 |
5/8 |
11 |
19200 |
14400 |
75 |
188 |
150 |
3/4 |
10 |
28400 |
21300 |
133 |
333 |
266 |
7/8 |
9 |
39250 |
29438 |
215 |
537 |
429 |
1 |
8 |
51500 |
38625 |
322 |
805 |
644 |
1 1/8 |
7 |
56450 |
42338 |
397 |
992 |
794 |
1 1/4 |
7 |
71700 |
53775 |
560 |
1400 |
1120 |
1 3/8 |
6 |
85450 |
64088 |
734 |
1836 |
1469 |
1 1/2 |
6 |
104000 |
78000 |
975 |
2438 |
1950 |
1 3/4 |
5 |
104500 |
78375 |
1143 |
2857 |
2286 |
2 |
4 1/2 |
137500 |
103125 |
1719 |
4297 |
3438 |
2 1/4 |
4 1/2 |
178750 |
134063 |
2514 |
6284 |
5027 |
2 1/2 |
4 |
220000 |
165000 |
3438 |
8594 |
6875 |
2 3/4 |
4 |
271150 |
203363 |
4660 |
11651 |
9321 |
3 |
4 |
328350 |
246263 |
6157 |
15391 |
12313 |
ASTM A193 B7
Bolt Size |
TPI |
Proof Load (lbs) |
Clamp Load (lbs) |
Tightening Torque (ft lbs) |
Waxed |
Galv |
Plain |
1/4 |
20 |
3350 |
2513 |
5 |
13 |
10 |
5/16 |
18 |
5500 |
4125 |
11 |
27 |
21 |
3/8 |
16 |
8150 |
6113 |
19 |
48 |
38 |
7/16 |
14 |
11150 |
8363 |
30 |
76 |
61 |
1/2 |
13 |
14900 |
11175 |
47 |
116 |
93 |
9/16 |
12 |
19100 |
14325 |
67 |
168 |
134 |
5/8 |
11 |
23750 |
17813 |
93 |
232 |
186 |
3/4 |
10 |
35050 |
26288 |
164 |
411 |
329 |
7/8 |
9 |
48500 |
36375 |
265 |
663 |
530 |
1 |
8 |
63650 |
47738 |
398 |
995 |
796 |
1 1/8 |
7 |
80100 |
60075 |
563 |
1408 |
1126 |
1 1/4 |
7 |
101750 |
76313 |
795 |
1987 |
1590 |
1 3/8 |
6 |
121300 |
90975 |
1042 |
2606 |
2085 |
1 1/2 |
6 |
147550 |
110663 |
1383 |
3458 |
2767 |
1 3/4 |
5 |
199500 |
149625 |
2182 |
5455 |
4364 |
2 |
4 1/2 |
262500 |
196875 |
3281 |
8203 |
6563 |
2 1/4 |
4 1/2 |
341250 |
255938 |
4799 |
11997 |
9598 |
2 1/2 |
4 |
420000 |
315000 |
6563 |
16406 |
13125 |
2 3/4 |
4 |
468500 |
351263 |
8050 |
20124 |
16100 |
3 |
4 |
567150 |
425363 |
10634 |
26585 |
21268 |
3 1/4 |
4 |
674500 |
505875 |
13701 |
34252 |
27402 |
3 1/2 |
4 |
791350 |
593513 |
17311 |
43277 |
34622 |
3 3/4 |
4 |
917700 |
688275 |
21509 |
53771 |
43017 |
4 |
4 |
1052600 |
789450 |
26315 |
65788 |
52630 |
ASTM A354-BD / ASTM A490 / SAE GRADE 8
Bolt Size |
TPI |
Proof Load (lbs) |
Clamp Load (lbs) |
Tightening Torque (ft lbs) |
Waxed |
Plain |
1/4 |
20 |
3800 |
2850 |
6 |
12 |
5/16 |
18 |
6300 |
4725 |
12 |
25 |
3/8 |
16 |
9300 |
6975 |
22 |
44 |
7/16 |
14 |
12750 |
9563 |
35 |
70 |
1/2 |
13 |
17050 |
12788 |
53 |
107 |
9/16 |
12 |
21850 |
16388 |
77 |
154 |
5/8 |
11 |
27100 |
20325 |
106 |
212 |
3/4 |
10 |
40100 |
30075 |
188 |
376 |
7/8 |
9 |
55450 |
41588 |
303 |
606 |
1 |
8 |
72700 |
54525 |
454 |
909 |
1 1/8 |
7 |
91550 |
68663 |
644 |
1287 |
1 1/4 |
7 |
120000 |
90000 |
938 |
1875 |
1 3/8 |
6 |
138600 |
103950 |
1191 |
2382 |
1 1/2 |
6 |
168600 |
126450 |
1581 |
3161 |
1 3/4 |
5 |
228000 |
171000 |
2494 |
4988 |
2 |
4 1/2 |
300000 |
225000 |
3750 |
7500 |
2 1/4 |
4 1/2 |
390000 |
292500 |
5484 |
10969 |
2 1/2 |
4 |
480000 |
360000 |
7500 |
15000 |
2 3/4 |
4 |
517650 |
388238 |
8897 |
17794 |
3 |
4 |
626850 |
470138 |
11753 |
23507 |
3 1/4 |
4 |
745500 |
559125 |
15143 |
30286 |
3 1/2 |
4 |
874650 |
655988 |
19133 |
38266 |
3 3/4 |
4 |
1014300 |
760725 |
23773 |
47545 |
4 |
4 |
1163400 |
872550 |
29085 |
58100 |
Notes:
- Values calculated using industry accepted formula T = KDP where T = Torque, K = torque coefficient (dimensionless), D = nominal diameter (inches), P = bolt clamp load, lb.
- K values: waxed (e.g. pressure wax as supplied on high strength nuts) = .10, hot dip galvanized = .25, and plain non-plated bolts (as received) = .20.
- Torque has been converted into ft/lbs by dividing the result of the formula by 12
- All calculations are for Coarse Thread Series (UNC).
- Grade 2 calculations only cover fasteners 1/4"-3/4" in diameter up to 6" long; for longer fasteners the torque is reduced significantly.
- Clamp loads are based on 75% of the minimum proof loads for each grade and size.
- Proof load, stress area, yield strength, and other data is based on IFI 7th Edition (2003) Technical Data N-68, SAE J429, ASTM A307, A325, A354, A449, and A490.