Bolt Torque & Preload Calculator

Estimate bolt preload from applied tightening torque.

Applied torque T (N·m)Nominal bolt diameter d (mm)Torque coefficient K (0.15–0.25 typical)Calculate

Equation

F = T / (K × d)

Assumptions

K lumps friction (thread + under-head) and geometry — verify for your fastener/lubrication condition. Does not check thread strip or joint stiffness.