Bolt Torque and Proof Load Reference

Proof load (kN) is the bolt’s rated axial clamping capacity per ISO 898-1 (proof stress × thread stress area) — 100% of rated capacity, not a working preload target; real preload targets are typically a percentage of this per your project’s bolting procedure. Torque is back-calculated from that fixed kN figure using the bolt condition selected above (T = K × D × F) — change the condition and only the torque columns move. M42 and above sit outside ISO 898-1’s core-tested size range; confirm those against the bolt’s own mill certificate. Every value here is a typical published reference figure, not a substitute for your project’s bolting procedure or the bolt manufacturer’s own data — always confirm before applying to actual work. Nothing you enter here is sent to or stored on our servers.