Bolt torque chart
Recommended tightening torque for common bolt sizes and grades, in imperial and metric. Values are for clean, dry threads, the standard reference condition. Lubricated threads need roughly 20-30% less torque for the same clamp force.
Inch bolts (clean, dry threads)
| Size | Grade 5 (lb-ft) | Grade 8 (lb-ft) |
|---|---|---|
| 1/4-20 | 8 | 12 |
| 5/16-18 | 17 | 25 |
| 3/8-16 | 31 | 44 |
| 7/16-14 | 49 | 70 |
| 1/2-13 | 76 | 106 |
| 9/16-12 | 111 | 153 |
| 5/8-11 | 152 | 212 |
| 3/4-10 | 271 | 376 |
| 7/8-9 | 437 | 606 |
| 1-8 | 654 | 908 |
Metric bolts (clean, dry threads)
| Size | Class 8.8 (Nm) | Class 10.9 (Nm) |
|---|---|---|
| M6 | 10 | 14 |
| M8 | 25 | 35 |
| M10 | 49 | 69 |
| M12 | 86 | 120 |
| M14 | 137 | 190 |
| M16 | 214 | 295 |
| M20 | 415 | 580 |
| M24 | 715 | 1000 |
Values are for clean, dry, plated steel fasteners at about 75% of proof load. Lubricated or anti-seized threads can need 20-30% less torque for the same tension. Always follow the manufacturer or engineering spec when one is given, and use a calibrated torque wrench.
Need a torque for a different size, grade, or lubrication?
The Bolt Torque Calculator works out torque from diameter, grade, friction, and target preload for any fastener.
How bolt torque works
Tightening a bolt stretches it slightly, and that stretch creates the clamping force that holds a joint together. Torque is the easiest way to reach a target tension, but most of it overcomes thread and head friction — only about 10 to 15 percent becomes clamp force. That is why lubrication, which lowers friction, sharply changes the torque needed.
Dry vs lubricated torque
These values assume clean, dry threads. Oil, grease, or anti-seize lowers friction, so the same torque produces more tension and can overload the bolt. If you lubricate, reduce the torque by roughly 20 to 30 percent, or use a value specified for that lubricant.
FAQ
What torque for a 1/2-13 Grade 8 bolt?
About 106 lb-ft on clean, dry threads. Reduce to roughly 75 to 85 lb-ft if the threads are lubricated.
Should bolt threads be oiled before torquing?
Only if the spec calls for it. Most dry-torque charts assume clean, dry threads; adding oil without lowering the torque can overstretch or snap the bolt.
Why does grade matter for torque?
Higher grades are stronger, so they can be tightened to a higher tension and torque. A Grade 8 bolt takes more torque than a Grade 5 of the same size.