Bolt Torque Reference
ReferenceStandard tightening torque for SAE and metric bolts by size, grade, and dry or lubed threads.
Not sure what to check first? Hand the result to the assistant.
About this tool
When there is no machine-specific figure to hand, this gives the standard torque for a bolt from its size, grade, and whether the threads are dry or lubricated. It targets 75% of the fastener's proof load - the normal clamp-load goal for a reusable joint - and converts that to a tightening torque in both lb-ft and N·m.
Pick SAE (inch) or metric, choose the diameter and grade or property class (Grade 2/5/8, or 8.8/10.9/12.9), and set the condition. Lubricated threads have a lower friction factor, so they reach the same clamp load at a lower torque - applying a dry-thread value to an oiled bolt over-stretches it.
These are computed from the SAE J429 and ISO 898-1 standard stress areas and proof strengths, not copied from any one chart. They are a general reference for shop and repair work. Structural connections, wheel nuts, track bolts, and cylinder-head bolts have specific torques and tightening sequences - always use the OEM value for those.
Frequently asked questions
Should bolt torque be dry or lubricated?
Match the actual condition of the threads. Plain, clean, dry threads use a nut factor around 0.20; oiled or anti-seize threads around 0.15. Because lubrication cuts friction, the lubricated torque is lower for the same clamp load. Using the wrong one either under-clamps or yields the bolt.
What does 75% of proof load mean?
Proof load is the highest tension a bolt can take without permanent stretch. Reusable joints are normally clamped to about 75% of that, leaving a margin. This tool uses 75%; some critical joints are torqued to yield instead, which needs the OEM procedure.
Can I use this for wheel nuts or track bolts?
Only as a rough sanity check. Wheels, tracks, and head bolts have specific OEM torques and tightening patterns that account for the joint design - always use the manual figure and sequence for those.
Why do bolt torque charts differ between sources?
Published charts vary with the exact nut factor, proof strength, and stress area they assume, plus rounding. A 5–10% spread between sources is normal. When precision matters, use a calibrated wrench and the OEM spec.
Does thread pitch change the torque?
Yes a little - fine threads have a slightly larger stress area than coarse for the same diameter, so they take a bit more torque. This tool uses the coarse (UNC / standard metric) series, which covers most heavy-equipment fasteners.