Enter the tensile stress area, major diameter of the screw, and pitch into the calculator to determine the minimum thread engagement length.

Thread Engagement Length Formula

The following equation is used to calculate the minimum Thread Engagement Length.

Le = 2*At / ( .5*pi*(D-.64952*p))

  • Where Le is the minimum thread engagement length (in)
  • At is the tensile stress area (in^2)
  • D is the diameter of the screw (in)
  • p is the thread pitch = 1/number of threads per inch

The units of measure for the minimum thread engagement length will be the same as the diameter.

What is a Thread Engagement Length?


A thread engagement length is considered the minimum viable length of thread that needs to be in contract with the opposite thread wall in order to handle a certain amount of stress.

How to Calculate ?

Example Problem:

The following example outlines the steps and information needed to calculate the Thread Engagement Length.

First, determine the tensile stress area. In this example the tensile stress area is found to be 2 in^2.

Next, determine diameter of the screw. This is measured to be .5 inches.

Next, determine the pitch of the screw. This is equal to the inverse of the threads per inch. In this case, the threads per inch is 5, so the pitch is 1/5.

Finally, calculate the minimum thread engagement length using the formula above:

Le = 2*At / ( .5*pi*(D-.64952*p))

Le = 2*2 / ( .5*3.14159*(.5-.64952*(1/5)))

Le = 6.88 in