Screw Torque Reference

Proper screw and bolt torque is critical for secure fastening without damaging threads or breaking the fastener. Under-torquing leads to loose joints, while over-torquing can strip threads or snap the bolt.

Torque unit conversions:

• 1 N-m (Newton-meter) = 0.7376 ft-lbs
• 1 ft-lb = 1.3558 N-m
• 1 N-m = 8.851 in-lbs
• 1 ft-lb = 12 in-lbs

Recommended torque for standard metric bolts (Grade 8.8, dry):

Recommended torque for imperial bolts (Grade 5, dry):

Grade, class, and the factors the calculator applies

The two tables above are the baseline: Grade 5 imperial and Class 8.8 metric, dry threads. Everything else is that figure multiplied by something, and these are the exact multipliers used above so the two can never disagree.

The lubrication one is the one people get wrong, and they get it wrong in the dangerous direction. Torque is a proxy for tension, and most of the torque you apply is spent fighting friction rather than stretching the bolt. Oil the threads and that friction drops, so the same reading on the wrench now means a much harder pull on the fastener. Applying a dry-spec torque to a lubricated bolt is a common way to snap it.

High-strength red threadlocker is not in the list because it changes removal, not installation. Plan on heat to get the bolt out again.

Material being fastened: soft materials like aluminum, plastic or thin sheet crush long before the bolt reaches its own limit. When the part is softer than the fastener, the part sets the torque.

Practical tips:

• Use a calibrated torque wrench for critical fasteners. Hand-feel is unreliable, especially for small bolts.
• Tighten bolts in a star or cross pattern when multiple bolts secure a single component (like cylinder heads or wheel lug nuts).
• Never use an impact driver for final torquing unless it has a calibrated torque-limiting mode.