Bolt Torque Calculator

About this calculator

This calculator applies the standard fastener torque formula T = K·D·F, where T is the required tightening torque, K is the nut factor (a dimensionless friction coefficient, typically around 0.2 for dry, uncoated steel but lower for lubricated or coated fasteners), D is the bolt's nominal diameter, and F is the target clamp (preload) force the joint needs to stay tight under load.

Mechanical engineers, machinists, and automotive and aerospace assemblers use torque-to-tension specifications like this to avoid two failure modes: under-torquing, which leaves a joint loose and prone to vibration loosening or fatigue, and over-torquing, which can yield or snap the bolt or crush a gasket. Enter the nut factor, diameter, and target clamp force to get the torque wrench setting.