How do I calculate Bolt Tightening Torque?

To calculate Bolt Tightening Torque: Enter Bolt size, Bolt grade, Utilisation factor ν and other values. Click Calculate. INDUGRID computes the result instantly using the formula: M_A = F_sp × d₂/2 × (tan λ + μ_G / cos α_n) + μ_K × F_sp × D_Km/2. No registration required.

What units does the Bolt Tightening Torque calculator use?

The Bolt Tightening Torque calculator uses the following units: %. SI units are used by default.

Is the Bolt Tightening Torque calculator free?

Yes. The INDUGRID Bolt Tightening Torque calculator is completely free, requires no account or login, and works on desktop and mobile browsers.

Mechanical Engineering

Bolt Tightening Torque

Calculate the required tightening torque for bolted connections based on bolt size, grade and desired preload force.

Units:

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💡Correct bolt torque is critical — under-torquing causes joint loosening and fatigue failure, over-torquing causes thread stripping or bolt breakage. Always use a calibrated torque wrench. Add thread locker (Loctite) for vibrating joints.

M_A = F_sp × d₂/2 × (tan λ + μ_G / cos α_n) + μ_K × F_sp × D_Km/2

Input

Bolt size iMetric bolt thread size.

Bolt grade iISO bolt property class. 8.8 is the most common industrial grade. 10.9 and 12.9 for high-strength applications.

Utilisation factor ν iPercentage of proof strength used as preload. Recommended: 70–90% for non-permanent joints, 90% for permanent.

Thread friction coefficient μ iThread and under-head friction. Dry steel: 0.12–0.18. Lightly oiled: 0.10–0.14. Zinc plated: 0.09–0.14.

Result

Preload force F_sp [kN] —

Tightening torque M_A [N·m] —

Min. torque (−10%) [N·m] —

Max. torque (+10%) [N·m] —