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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).