Bolt Torque Calculator

The SkyCiv Bolt Torque Calculator is a free tool to help determine the correct amount of rotational force needed to tighten a bolt. Torque is a measure of the conversion of linear force to rotational force at a distance from the axis of rotation. The below tool can also be used as a clamping force calculator when the clamp force option is selected in the input panel.

For engineers, torque is important for connections that bolt or clamp two materials or members together. When Torque is applied to a bolt, this force becomes tension in the bolt threads, which in turn applies a clamping force (or load) between the two materials you are bolting together.

Starting SkyCiv Bolt Torque Calculator...

How to calculate Bolt Torque

How to use the bolt preload torque calculator?

To get started with this bolt torque calculator you will need a few details handy. The first of these factors is the K Constant which is the factor that considers the frictional characteristics of the bolt and connected components. The bolt diameter is also required. Additionally, the lubrication factor can also be included in this calculator. Finally, the torque or clamping force applied to the bolt is required before running the bolt calculation.

What limitations does the bolt torque calculator have?

The SkyCiv Bolt Preload Calculator has a few limitations that it is important to be aware of when using. The first limitation is that the calculations completed are done in metric units, however; automatic unit conversion is available. Bolt threading considerations are not included in this calculator. Finally, the formula used in this calculator is an approximation, as it does not take into account the bolt thread pitch (the angle and density of threads). Please also note that the accuracy of most torque wrenches is around +-25%.

What is the formula for a bolt torque calculation?

The formula used in this calculator is:


  • K - Nut Factor Constant Dependant on the Bolt Size and Material
  • d - Diameter of Bolt (in mm)
  • ct - Lubrication Coefficient
  • F - Clamp Force (in N-m)

How to use the bolt clamping force calculator?

To use this calculator to calculate clamping force first switch the "Calculate" input to the "Clamp Force" option. This will then adjust the calculator to determine the bolt clamping force based on the inputted torque value. Bolt clamping force is an important part of structural connection design as it prevents two separate members moving or separating when joined together.

What is the formula for a clamping force calculation?

The formula used in this calculator is the clamping force formula. The formula is:

Clamp Force Calculator


  • K - Nut Factor Constant Dependant on the Bolt Size and Material
  • d - Diameter of Bolt (in mm)
  • ct - Lubrication Coefficient
  • T - Torque or Force (in N)

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Clamp Force Calculator FAQs

Why is bolt torque important?

Bolt torque is important to ensure that the correct amount of clamping torque is applied to a bolted joint. By using a bolt torque calculator engineers can make sure that integrity, performance, and tightening of bolted joints remain consistent across multiple connections.

What factors affect bolt torque?

Multiple factors can affect bolt torque including bolt diameter, bolt threading, material properties, and lubrication. By adding these factors to the bolt torque force calculator above you can easily determine the torque on a bolt.

Where can I find torque specifications?

Bolt manufacturers as well as engineering standards often contain torque specifications that can be used alongside this calculator.

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