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Bolt Root and Tensile Stress Area

Fastener and Screw / Bolt Design, Formula & Calculations

Bolt Root and Tensile Stress Area Table for Metric and Inch Unit Threads

SI Metric Units
Bolt Size, Basic Thread Designation [Notes(1),(2)]	Root Area, mm2	Tensile Stress Area, mm2 [Note(3)]
M14-2	102.1	115.4
M16-2	141.0	156.7
M20-2.5	220.4	244.8
M24-3	317.3	352.5
M27-3	419.1	459.4
M30-3	535.0	580.4
M33-3	665.1	715.6
M36-3	809.3	864.9
M39-3	976.6	1028
M42-3	1140	1206
M45-3	1327	1398
M48-3	1527	1604
M52-3	1817	1900
M56-3	2132	2222
M64-3	2837	2940
M70-3	3432	3545
M76-3	4083	4207
M82-3	4791	4925
M90-3	5822	5970
M95-3	6518	6674
M100-3	7253	7418

 

U.S.Customary Inch Units
Bolt Size, in.	Threads per Inch		Root Area, in.2	Tensile Stress
				Area ,in.2
				[Note(3)]
1⁄2	13		0.1257	0.1419
5⁄8	11		0.2017	0.2260
3⁄4	10		0.3019	0.3345
7⁄8	9		0.4192	0.4617
1	8		0.5509	0.6057
1 - 1⁄8	8		0.7276	0.7905
1 - 1⁄4	8		0.9289	0.9997
1 - 3⁄8	8		1.155	1.234
1 - 1⁄2	8		1.405	1.492
1 - 5⁄8	8		1.680	1.775
1 - 3⁄4	8		1.979	2.082
1 - 7⁄8	8		2.303	2.414
2	8		2.652	2.771
2 - 1⁄4	8		3.422	3.557
2 - 1⁄2	8		4.291	4.442
2 - 3⁄4	8		5.258	5.425
3	8		6.324	6.506
3 - 1⁄4	8		7.487	7.686
3 - 1⁄2	8		8.748	8.963
3 - 3⁄4	8		10.11	10.34
4	8		11.57	11.81

NOTES:
(1) Metric thread designations are given in bolt size (mm) and pitch (mm) (e.g., M14-2 refers to a 14 mm diameter bolt with a 2 mm pitch thread).
(2) The side-by-side placement of the two tables is not meant to infer direct conversion between the listed SI and U.S. Customary units.
(3) The root and tensile stress areas are based on coarse-thread series for sizes M27 and smaller, and 3 mm pitch thread series for sizes
M30 and larger (coarse-thread series for sizes 1 in. and smaller, and 8-pitch thread series for sizes 1- 1⁄8 in. and larger).