Bolt Torque Calculator
Find the tightening torque that gives the clamp force you want from a metric coarse bolt. Choose the size, property class and how the threads are lubricated.
Results
Tightening torque:
- Torque in lbf·ft
- Clamp force (preload)
- Proof load of the bolt
- Tensile stress area
- Proof strength
Proof load = proof strength × stress area. Preload = chosen % of proof load. Torque T = K × preload × nominal diameter.
The nut factor sums up thread and underhead friction, so real torque values can vary by ±25% or more. For critical joints, follow the fastener maker's data or measure the bolt stretch. Torques here are for steel nuts and washers at room temperature.
Torque table for the chosen class and thread condition
| Size | Stress area, mm² | Proof load, kN | Preload, kN | Torque, N·m |
|---|