Bolt Torque Calculator
Torque spec for any bolt grade + size
📚 Learn more — how it works, FAQ & guide Click to expand
Learn more — how it works, FAQ & guide
Click to expand
Bolt torque calculator
Find torque spec for any bolt size, grade, lubrication.
How to use this tool
- 1
Pick bolt size + grade
Diameter + strength class determine proof load.
- 2
Pick lubrication
Dry, lubricated, or anti-seize (friction factor).
- 3
See torque spec
Recommended torque in ft·lb and N·m.
Frequently Asked Questions
Torque formula
T = K × D × F, where K = friction coeff (0.2 dry, 0.15 lube), D = bolt diameter, F = preload force (~75% of proof load).
Grade meanings
SAE Grade 5: medium strength. Grade 8: high strength. Metric 8.8: ~Grade 5. Metric 10.9/12.9: high strength.
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