Bolt Torque Calculator
Construction & Home ImprovementEstimate the tightening torque needed to achieve a target clamp force on a bolt, based on bolt diameter and surface condition.
Estimated Torque
Estimated tightening torque in foot-pounds.
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Construction & Home Improvement calculators
Calculator Stats
Creators
Odeh Ahwal0people find this calculator helpful
Views
Helpful
Saved
Embeds
Construction & Home Improvement calculators
Frequently Asked Questions
How accurate is this torque estimate?
This uses the standard T equals K times D times F formula with typical published friction, or nut factor, values. Real-world nut factors can vary by roughly plus or minus 25 percent even for the same stated condition, since actual friction depends on the specific lubricant, coating thickness, and surface finish. For a critical or safety-related joint, use torque-tension testing or the fastener manufacturer specific torque chart rather than relying on this estimate alone.
What nut factor does each surface condition use?
Dry or plain steel uses 0.20, lubricated uses 0.125, zinc-plated uses 0.21, and hot-dip galvanized uses 0.25, all typical published values.
Why does a lubricated bolt need less torque for the same clamp force?
Lubrication reduces friction under the bolt head and in the threads, so more of the applied torque converts into actual clamping force instead of being lost to friction.
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