How to calculate force for every screw thread

Written by jamie peacock
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How to calculate force for every screw thread
Calculating the force for a screw usually comes down to mathematics. (screw image by Dariusz Urbanczyk from

Calculating the force for every screw thread falls more under physics than it does home repair. This involves torque-tension relationships, and these may change based on variables. You may need to make this calculation to make sure you have the right tools and can apply the correct force for the project that you are working on.

Skill level:

Things you need

  • Screw
  • Formula or computer program

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  1. 1

    Pick out the screw that you will be measuring. Keep the packaging if you have it so you can reference it for measurements.

  2. 2

    Determine the measurements of the screw. This will include the thread size, finish and yield strength. These measurements should be listed on the packaging for the screw. Finding the force of the screw will be much more accurate if you have these parameters available.

  3. 3

    Measure the screw if you do not have the measurements available. You may have to guess as to the finish and yield strength. This will decrease the accuracy of the results. An engineering book may have the measurements listed, based on standard parameters.

  4. 4

    Enter the measurements into an online formula calculator. If you do not have access to one, you can manually find the force for every screw thread. One formula is T = DKF, with T being torque, D being diameter or thread size, K being the nut factor -- i.e., finish -- and F being the force -- i.e., yield strength.

Tips and warnings

  • Some programs, such as TORKSense have a database of standard screws and other fasteners.
  • Calculating the force for every screw thread is not an exact science because of the many variables that will change the results.

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