Enter the coefficient of friction, cable weight per unit length, and run length into the calculator to estimate the wire pull force for a straight run (no bends). Use the “Max Allowable Tension” tab to estimate maximum allowable pulling tension using the common NEC rule of thumb.

Cable Pulling Calculator

Estimate route pull tension, bend multiplier, sidewall pressure, and allowable pulling tension.

Route Pull Tension
Allowable Tension

Use this for an actual cable pull estimate. It combines straight-run friction with bend tension growth.

PVC + lube 0.20
PVC dry 0.35
Steel dry 0.50

Example: 180° for two 90° bends.

Use this to estimate maximum allowable pulling tension from conductor area and material factor.

Copper 0.008
Aluminum 0.006

Example: 1/0 AWG is about 105600 cmil.

Max straight length uses: (allowable tension – entry tension) / (friction × cable weight).

Wire Pull Force Formula

The following equation can be used to estimate the wire pull force for a straight, level run (no bends).

WPF = u*w*L
  • Where WPF is the wire pull force (lbs)
  • u is the coefficient of friction
  • w is the cable weight per unit length (lb/ft)
  • L is the length of the run (ft)

What is a Wire Pull Force?

Definition:

A wire pull force (pulling tension) is the amount of force it takes to pull a wire or cable through a raceway. In other words, it's the amount of force needed to pull a wire through a conduit, or through a hole in a wall filled with cable.

How to Calculate Wire Pull Force?

Example Problem:

The following example outlines the steps and information needed to estimate Wire Pull Force for a straight, level run.

First, determine the coefficient of friction. For this example, the coefficient of friction is 0.35.

Next, determine the cable weight per unit length. For this example, the cable weight is 2.0 lb/ft.

Next, determine the length of the run. The run length is 150 ft.

Finally, calculate the wire pull force using the formula above:

WPF = u*w*L

WPF = 0.35*2.0*150

WPF = 105 lbs