Bolt Pretension Calculation
Bolt pretension and bolt preload usually mean the same installed tensile force in the fastener. Calculate it from torque with F = T/(K*d).
bolt pretension calculation bolt pretension formula bolt pretension from torque
Pretension equation
F = T / (K * d)
Terminology
Pretension, preload and clamp force are often used interchangeably for the installed tension in the bolt after tightening.
Worked example
A 30 N*m torque on M10 with K = 0.20 gives about 15 kN pretension.
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.