Enter the nominal diameter (in), the desired clamp load (lbf), and the coefficient of friction into the calculator to determine the Fastener Torque. 

Fastener Torque Formula

The following formula is used to calculate the Fastener Torque.

Tf = (D*P*K) / 12

  • Where Tf is the Fastener Torque (lbf-ft)
  • D is the nominal diameter (in) 
  • P is the desired clamp load (lbf) 
  • K is the coefficient of friction 

How to Calculate Fastener Torque?

The following example problems outline how to calculate Fastener Torque.

Example Problem #1

  1. First, determine the nominal diameter (in). In this example, the nominal diameter (in) is determined to be .25 .
  2. Next, determine the desired clamp load (lbf). For this problem, the desired clamp load (lbf) is measured to be 500 .
  3. Next, determine the coefficient of friction. In this case, the coefficient of friction is found to be .85.
  4. Finally, calculate the Fastener Torque using the formula above: 

Tf = (D*P*K) / 12

Inserting the values from above and solving yields: 

Tf = (.25*500*.85) / 12 = 8.85 (lbf-ft)

Example Problem #2

Using the same method as above, determine the variables required by the formula. For this example problem, these are:

nominal diameter (in) = .75

desired clamp load (lbf) = 900

coefficient of friction = .40

Enter these given values yields: 

Tf = (.75*900*.40) / 12 = 22.5 (lbf-ft)