Bolt torque equation

Torque/tension relationship

Guide to the Design Consideration on the Strength of Screw Threads

T = P o     ( E s 2 tan ( λ )   + E s 2 μ 1 cos ( α )   +   d o + d i 4 μ 2 )
= P o     ( p 2 π   + E s 2 μ 1 cos ( α )   +   d o + d i 4 μ 2 )