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Bolt Torque Chart

Bolted connections are critical components in structural and mechanical systems. Proper tensioning and torque application ensures joint integrity, load distribution, and resistance to fatigue and vibration. This reference consolidates key data for standard bolt sizes, including:

Proof Load: The maximum tensile load a bolt can withstand without permanent deformation, in accordance with ASTM specifications.
Clamp Load: The tensile force applied to a bolt to achieve proper joint compression; essential for preventing joint separation and ensuring consistent preload.
Tightening Torque: Recommended torque ranges for both plain and lubricated threads to achieve target clamp loads. Improper torque can lead to underloading (joint slippage) or overloading (bolt failure).

Technical Considerations

Torque values assume standard ASTM-compliant threads and materials. Variations in surface finish, coating, or thread lubrication require adjustments.
Lubrication significantly reduces friction; recommended torque is roughly 50% of the plain value for equivalent preload.
Bolt elongation during tightening is proportional to clamp load; always consider joint stiffness to avoid exceeding proof load.
TPI (Threads per Inch) affects torque-to-load conversion: finer threads achieve higher clamp load at the same torque.
Always account for environmental factors (temperature, corrosion, vibration) that may influence preload retention.

Application Notes

Structural steel assemblies (A325/A490) should follow the torque and tension ranges listed for high-strength bolts.
For critical applications (bridges, heavy machinery, pressure vessels), use calibrated torque wrenches and consider verification via ultrasonic or load-indicating methods.
When in doubt, always consult ASTM, ISO, or manufacturer-specific guidelines for bolt materials and joint types.

ASTM A307

Bolt Size	TPI	Proof Load (lbs)¹	Clamp Load (lbs)²	Tightening Torque (ft lbs)
Bolt Size	TPI	Proof Load (lbs)¹	Clamp Load (lbs)²	Galv+Waxed	Galv	Plain
1⁄4	20	1,053	790	2	4	3
5⁄16	18	1,735	1,302	3	8	7
3⁄8	16	2,567	1,925	6	15	12
7⁄16	14	3,521	2,640	10	24	19
1⁄2	13	4,700	3,525	15	37	29
9⁄16	12	6,028	4,521	21	53	42
5⁄8	11	7,485	5,614	29	73	58
3⁄4	10	11,062	8,297	52	130	104
7⁄8	9	15,301	11,476	84	209	167
1	8	20,071	15,053	125	314	251
11⁄8	7	25,271	18,953	178	444	355
11⁄4	7	32,093	24,070	251	627	501
13⁄8	6	38,254	28,690	329	822	657
11⁄2	6	46,534	34,900	436	1,091	873
13⁄4	5	62,928	47,196	688	1,721	1,377
2	4 1⁄2	82,800	62,100	1,035	2,588	2,070
21⁄4	4 1⁄2	107,640	80,730	1,514	3,784	3,027
21⁄2	4	132,480	99,360	2,070	5,125	4,140
23⁄4	4	163,282	122,461	2,806	7,016	5,613
3	4	197,726	148,295	3,707	9,268	7,415
31⁄4	4	235,152	176,364	4,777	11,941	9,553
31⁄2	4	275,890	206,917	6,035	15,088	12,070
33⁄4	4	319,939	239,954	7,499	18,746	14,997
4	4	366,970	275,227	9,174	22,936	18,348

SAE Grade 2

Bolt Size	TPI	Proof Load (lbs)¹	Clamp Load (lbs)²	Tightening Torque (ft lbs)
Bolt Size	TPI	Proof Load (lbs)¹	Clamp Load (lbs)²	Galv+Waxed	Galv	Plain
1⁄4	20	1,750	1,313	3	7	5
5⁄16	18	2,900	2,175	6	14	11
3⁄8	16	4,250	3,188	10	25	20
7⁄16	14	5,850	4,388	16	40	32
1⁄2	13	7,800	5,850	24	61	49
9⁄16	12	10,000	7,500	35	88	70
5⁄8	11	12,400	9,300	48	121	97
3⁄4	10	18,400	13,800	86	216	173
7⁄8	9	15,200	11,400	83	208	166
1	8	20,000	15,000	125	313	250
11⁄8	7	25,200	18,900	177	443	354
11⁄4	7	32,000	24,000	250	625	500
13⁄8	6	38,100	28,575	327	819	655
11⁄2	6	46,400	34,800	435	1,088	870

ASTM A325

Bolt Size	TPI	Tension		Tightening Torque Range (ft lbs) (Min - Max)
Bolt Size	TPI	Min	Max	Galv+Waxed	Plain
1⁄2	13	12,000	14,000	50 - 58	100 - 117
5⁄8	11	19,000	23,000	99 - 120	198 - 240
3⁄4	10	28,000	34,000	175 - 213	350 - 425
7⁄8	9	39,000	47,000	284 - 343	569 - 685
1	8	51,000	61,000	425 - 508	850 - 1,017
11⁄8	7	64,000	77,000	600 - 722	1,200 - 1,444
11⁄4	7	81,000	98,000	844 - 1,021	1,687 - 2,042
13⁄8	6	97,000	117,000	1,111 - 1,341	2,223 - 2,681
11⁄2	6	118,000	143,000	1,475 - 1,788	2,950 - 3,575

ASTM A449 / SAE Grade 5

Bolt Size	TPI	Proof Load (lbs) 1	Clamp Load (lbs) 2	Tightening Torque (ft lbs)
Bolt Size	TPI	Proof Load (lbs) 1	Clamp Load (lbs) 2	Galv+Waxed	Galv	Plain
1⁄4	20	2,700	2,025	4	11	8
5⁄16	18	4,450	3,338	9	22	17
3⁄8	16	6,600	4,950	15	39	31
7⁄16	14	9,050	6,788	25	62	49
1⁄2	13	12,050	9,038	38	94	75
9⁄16	12	15,450	11,588	54	136	109
5⁄8	11	19,200	14,400	75	188	150
3⁄4	10	28,400	21,300	133	333	266
7⁄8	9	39,250	29,438	215	537	429
1	8	51,500	38,625	322	805	644
11⁄8	7	56,450	42,338	397	992	794
11⁄4	7	71,700	53,775	560	1,400	1,120
13⁄8	6	85,450	64,088	734	1,836	1,469
11⁄2	6	104,000	78,000	975	2,438	1,950
13⁄4	5	104,500	78,375	1,143	2,857	2,286
2	4 1⁄2	137,500	103,125	1,719	4,297	3,438
21⁄4	4 1⁄2	178,750	134,063	2,514	6,284	5,027
21⁄2	4	220,000	165,000	3,438	8,594	6,875
23⁄4	4	271,150	203,363	4,660	11,651	9,321
3	4	328,350	246,263	6,157	15,391	12,313

ASTM A193 B7 / ASTM A320 L7 / ASTM A354 BC

Bolt Size	TPI	Proof Load (lbs) 1	Clamp Load (lbs) 2	Tightening Torque (ft lbs)
Bolt Size	TPI	Proof Load (lbs) 1	Clamp Load (lbs) 2	Galv+Waxed	Galv	Plain
1⁄4	20	3,350	2,513	5	13	10
5⁄16	18	5,500	4,125	11	27	21
3⁄8	16	8,150	6,113	19	48	38
7⁄16	14	11,150	8,363	30	76	61
1⁄2	13	14,900	11,175	47	116	93
9⁄16	12	19,100	14,325	67	168	134
5⁄8	11	23,750	17,813	93	232	186
3⁄4	10	35,050	26,288	164	411	329
7⁄8	9	48,500	36,375	265	663	530
1	8	63,650	47,738	398	995	796
11⁄8	7	80,100	60,075	563	1,408	1,126
11⁄8	8	82,934	62,201	583	1,458	1,166
11⁄4	7	101,750	76,313	795	1,987	1,590
11⁄4	8	105,006	78,754	820	2,051	1,641
13⁄8	6	121,300	90,975	1,042	2,606	2,085
13⁄8	8	129,492	97,119	1,113	2,782	2,226
11⁄2	6	147,550	110,663	1,383	3,458	2,767
11⁄2	8	156,687	117,515	1,469	3,672	2,938
13⁄4	5	199,500	149,625	2,182	5,455	4,364
13⁄4	8	218,400	163,800	-	-	4,778
2	41⁄2	262,500	196,875	3,281	8,203	6,563
2	8	290,850	218,138	-	-	7,271
21⁄4	41⁄2	341,250	255,938	4,799	11,997	9,598
21⁄4	8	373,801	280,351	-	-	10,513
21⁄2	4	420,000	315,000	6,563	16,406	13,125
21⁄2	8	466,200	349,650	-	-	14,569
23⁄4	4	468,500	351,263	8,050	20,124	16,100
23⁄4	8	515,851	386,888	-	-	17,732
3	4	567,150	425,363	10,634	26,585	21,268
3	8	618,451	463,838	-	-	23,192
31⁄4	4	674,500	505,875	13,701	34,252	27,402
31⁄4	8	730,550	547,913	-	-	29,679
31⁄2	4	791,350	593,513	17,311	43,277	34,622
31⁄2	8	851,201	638,401	-	-	37,240
33⁄4	4	917,700	688,275	21,509	53,771	43,017
33⁄4	8	982,300	736,725	-	-	46,045
4	4	1,052,600	789,450	26,315	65,788	52,630
4	8	1,121,950	841,463	-	-	56,098

ASTM A490

Bolt Size	TPI	Tension (lbs)		Tightening Torque Range (ft lbs) (Min - Max)
Bolt Size	TPI	Min	Max	Plain	Lubricated
1⁄2	13	15,000	18,000	125 - 150	63 - 75
5⁄8	11	24,000	29,000	250 - 302	125 - 151
3⁄4	10	35,000	42,000	438 - 525	219 - 263
7⁄8	9	49,000	59,000	715 - 860	357 - 430
1	8	64,000	77,000	1,067 - 1,283	533 - 642
11⁄8	7	80,000	96,000	1,500 - 1,800	750 - 900
11⁄4	7	102,000	122,000	2,125 - 2,542	1,063 - 1,271
13⁄8	6	121,000	145,000	2,773 - 3,323	1,386 - 1,661
11⁄2	6	148,000	178,000	3,700 - 4,450	1,850 - 2,225

ASTM A354-DB / SAE Grade 8

Bolt Size	TPI	Proof Load (lbs)	Clamp Load (lbs)	Tightening Torque (ft lbs)
Bolt Size	TPI	Proof Load (lbs)	Clamp Load (lbs)	Plain	Lubricated
1⁄4	20	3,800	2,850	12	6
5⁄16	18	6,300	4,725	25	12
3⁄8	16	9,300	6,975	44	22
7⁄16	14	12,750	9,563	70	35
1⁄2	13	17,050	12,788	107	53
9⁄16	12	21,850	16,388	154	77
5⁄8	11	27,100	20,325	212	106
3⁄4	10	40,100	30,075	376	188
7⁄8	9	55,450	41,588	606	303
1	8	72,700	54,525	909	454
11⁄8	7	91,550	68,663	1,287	644
11⁄4	7	120,000	90,000	1,875	938
13⁄8	6	138,600	103,950	2,382	1,191
11⁄2	6	168,600	126,450	3,161	1,581
13⁄4	5	228,000	171,000	4,988	2,494
2	4 1⁄2	300,000	225,000	7,500	3,750
21⁄4	4 1⁄2	390,000	292,500	10,969	5,484
21⁄2	4	480,000	360,000	15,000	7,500
23⁄4	4	517,650	388,238	17,794	8,897
3	4	626,850	470,138	23,507	11,753
31⁄4	4	745,500	559,125	30,286	15,143
31⁄2	4	874,650	655,988	38,266	19,133
33⁄4	4	1,014,300	760,725	47,545	23,773
4	4	1,163,400	872,550	58,100	29,085

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.