Enter the tightening factor, axial force, and bolt diameter into the calculator to determine the flange bolt torque.

## Flange Bolt Torque Formula

The following formula is used to calculate a flange bolt torque:

T = k * f * d / 12
• Where T is the flange bolt torque (ft-lb)
• k is the tightening factor
• f is the axial force (lbs)
• d is the diameter of the bolt (inches).

To calculate the flange bolt torque, multiply the tightening factor by the axial force and the diameter, then divide by 12.

## What is a flange bolt torque?

The flange bolt torque is the total torque that a flange bolt is subjected to when being tightened by a wrench.

The total torque required to tighten the bolt is dependent on the axial force seen by the bolt, the diameter, the tightening factor.

A tightening factor is a ratio or factor of safety that the bolt needs to be tightened to in order to sustain the axial load forces on the bolt.

## How to claculate flange bolt torque?

The following example shows the steps and information needed to calculate a flange bolt torque.

First, determine the diameter of the bolt. In this example, the bolt has a diameter of 3 inches.

Next, determine the axial force seen by the bolt. In this example problem, the axial force on the bolt is measured to be 500 lbs-f.

Next, determine the tightening/nut factor. For this problem, the nut factor is 2.5.

Finally, calculate the flange bolt torque using the formula above:

T = k * f * d / 12

T = 2.5 * 500* 3 / 12

T = 312.5 ft-lbs