Standard Bolt Torque Values
These are recommended tightening torques for standard dry (unlubricated) bolts. If you’re using lubricant, anti-seize, or plating, reduce torque by 25–30% — lubrication dramatically changes the torque-tension relationship.
Grade 5 Bolts — Torque Values
| Bolt Size | TPI (UNC) | Clamp Load (lbs) | Torque Dry (ft-lbs) | Torque Lubed (ft-lbs) |
|---|---|---|---|---|
| 1/4-20 | 20 | 2,025 | 6.3 | 4.7 |
| 5/16-18 | 18 | 3,340 | 13 | 10 |
| 3/8-16 | 16 | 4,950 | 23 | 18 |
| 7/16-14 | 14 | 6,780 | 37 | 28 |
| 1/2-13 | 13 | 9,050 | 57 | 43 |
| 9/16-12 | 12 | 11,600 | 82 | 62 |
| 5/8-11 | 11 | 14,400 | 113 | 85 |
| 3/4-10 | 10 | 21,300 | 200 | 150 |
| 7/8-9 | 9 | 29,500 | 322 | 242 |
| 1-8 | 8 | 38,700 | 483 | 362 |
Grade 8 Bolts — Torque Values
| Bolt Size | TPI (UNC) | Clamp Load (lbs) | Torque Dry (ft-lbs) | Torque Lubed (ft-lbs) |
|---|---|---|---|---|
| 1/4-20 | 20 | 2,860 | 9 | 6.7 |
| 5/16-18 | 18 | 4,720 | 18 | 14 |
| 3/8-16 | 16 | 6,990 | 33 | 25 |
| 7/16-14 | 14 | 9,580 | 52 | 39 |
| 1/2-13 | 13 | 12,770 | 80 | 60 |
| 9/16-12 | 12 | 16,400 | 115 | 86 |
| 5/8-11 | 11 | 20,400 | 159 | 119 |
| 3/4-10 | 10 | 30,100 | 282 | 211 |
| 7/8-9 | 9 | 41,600 | 454 | 341 |
| 1-8 | 8 | 54,600 | 682 | 511 |
18-8 Stainless Steel Bolts — Torque Values
| Bolt Size | TPI (UNC) | Torque Dry (ft-lbs) | Torque Lubed (ft-lbs) |
|---|---|---|---|
| 1/4-20 | 20 | 5.5 | 4.2 |
| 5/16-18 | 18 | 11 | 8 |
| 3/8-16 | 16 | 20 | 15 |
| 1/2-13 | 13 | 50 | 38 |
| 5/8-11 | 11 | 98 | 74 |
| 3/4-10 | 10 | 173 | 130 |
| 1-8 | 8 | 420 | 315 |
Critical Torque Rules
- Lubrication changes everything. Anti-seize or oil reduces friction so the same torque produces ~30% more clamp load. Over-torquing lubed bolts is the #1 cause of bolt failure.
- These are for 75% of proof load. Standard industry practice — provides a safety margin while achieving adequate clamping force.
- Torque ≠ tension. Torque is a proxy for clamping force. 90% of the torque goes to overcoming friction — only 10% actually stretches the bolt. For critical joints, use bolt stretch measurement or ultrasonic testing.
- Re-torque after initial loading. Embedment relaxation (surfaces settling) can reduce clamp load by 5–10% after first loading. Re-torque once for critical connections.
- Never reuse torque-to-yield bolts. If the spec calls for “torque plus angle” (TTY), the bolt is designed to be stretched past its elastic limit. Replace every time.
Torque Formula
T = K × F × D
- T = torque (in-lbs)
- K = nut factor (0.20 dry, 0.15 lubed, 0.12 anti-seize, varies by condition)
- F = desired clamp load (lbs)
- D = nominal bolt diameter (in)
Related: Bolt Grade Identification | Hex Cap Bolt Dimensions | Hex Nut Dimensions