Torque-Tension Equation
The torque-tension equation relates tightening torque to bolt preload through nominal diameter and nut factor.
torque tension equation torque to tension formula bolt torque tension
Equation
T = K * d * F
Solve either direction
- Preload from torque: F = T / (K * d).
- Torque from target preload: T = K * d * F.
Why K dominates
Most tightening torque is lost to friction under the head and in the threads, so finish and lubricant change delivered tension.
Related pages
- Bolt preload torque calculator - calculate clamp force, proof-load utilization and preload scatter.
- Bolt preload formula - equation and nut-factor definitions.
- Bolt preload explained - joint mechanics, proof load targets and preload scatter.
- Bolt torque spec chart - starting torque values by size and grade.