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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).