Torque Table & Equations



Download a PDF version of the chart here.

The above torque table was developed and simplified for marine applications, and is based on material strength.


Torque Table Equations

First, the units:

$$TPI$$  Threads Per Inch

$$d_{nom}$$  Nominal diameter

$$A_t$$  Tensile Stress Area

$$F_y$$  Yield Strength

$$F_i$$  Preload

$$S_p$$  Proof Strength

$$K$$  Coefficient of friction (=0.15 for lubricated screws)


To determine Preload:

$$F_i=0.75F_p$$  for non permanent connections1.


$$S_p=0.85F_y$$  for proof strength

To calculate bolt torque:


Which can also be written as:



  1.  Shigley’s Machine Design, 1998.  p. 427 (Eq. 8-30)
  2.  Shigley’s Machine Design, 1998.  p. 423 (Eq. 8-27)