Bolt torque chart.
Recommended tightening torque for common bolts — Grade 5/8 imperial and Grade 8.8/10.9/12.9 metric.
Recommended tightening torque for common bolts — Grade 5/8 imperial and Grade 8.8/10.9/12.9 metric. Dry, lubricated, and anti-seize values. Derived from the standard K-factor formula T = K × D × P.
The chart
| Size | Grade | Dry (K=0.20) | Lubricated (K=0.15) | Anti-seize (K=0.10) |
|---|---|---|---|---|
| 1/4-20 | Grade 5 | 8 ft·lbf | 6 ft·lbf | 5 ft·lbf |
| 5/16-18 | Grade 5 | 17 ft·lbf | 13 ft·lbf | 10 ft·lbf |
| 3/8-16 | Grade 5 | 30 ft·lbf | 23 ft·lbf | 17 ft·lbf |
| 7/16-14 | Grade 5 | 50 ft·lbf | 38 ft·lbf | 28 ft·lbf |
| 1/2-13 | Grade 5 | 75 ft·lbf | 57 ft·lbf | 43 ft·lbf |
| 9/16-12 | Grade 5 | 110 ft·lbf | 83 ft·lbf | 62 ft·lbf |
| 5/8-11 | Grade 5 | 150 ft·lbf | 113 ft·lbf | 85 ft·lbf |
| 3/4-10 | Grade 5 | 270 ft·lbf | 203 ft·lbf | 152 ft·lbf |
| 7/8-9 | Grade 5 | 435 ft·lbf | 326 ft·lbf | 245 ft·lbf |
| 1-8 | Grade 5 | 650 ft·lbf | 488 ft·lbf | 366 ft·lbf |
| 1/4-20 | Grade 8 | 12 ft·lbf | 9 ft·lbf | 6 ft·lbf |
| 5/16-18 | Grade 8 | 24 ft·lbf | 18 ft·lbf | 13 ft·lbf |
| 3/8-16 | Grade 8 | 43 ft·lbf | 32 ft·lbf | 24 ft·lbf |
| 7/16-14 | Grade 8 | 70 ft·lbf | 53 ft·lbf | 40 ft·lbf |
| 1/2-13 | Grade 8 | 105 ft·lbf | 79 ft·lbf | 60 ft·lbf |
| 9/16-12 | Grade 8 | 155 ft·lbf | 116 ft·lbf | 87 ft·lbf |
| 5/8-11 | Grade 8 | 210 ft·lbf | 158 ft·lbf | 118 ft·lbf |
| 3/4-10 | Grade 8 | 375 ft·lbf | 281 ft·lbf | 211 ft·lbf |
| 7/8-9 | Grade 8 | 610 ft·lbf | 458 ft·lbf | 343 ft·lbf |
| 1-8 | Grade 8 | 910 ft·lbf | 683 ft·lbf | 512 ft·lbf |
| M4 × 0.7 | 8.8 | 3 N·m | 2 N·m | 2 N·m |
| M5 × 0.8 | 8.8 | 6 N·m | 5 N·m | 4 N·m |
| M6 × 1.0 | 8.8 | 11 N·m | 8 N·m | 6 N·m |
| M8 × 1.25 | 8.8 | 26 N·m | 20 N·m | 15 N·m |
| M10 × 1.5 | 8.8 | 53 N·m | 40 N·m | 30 N·m |
| M12 × 1.75 | 8.8 | 92 N·m | 69 N·m | 52 N·m |
| M14 × 2.0 | 8.8 | 146 N·m | 110 N·m | 83 N·m |
| M16 × 2.0 | 8.8 | 229 N·m | 172 N·m | 129 N·m |
| M20 × 2.5 | 8.8 | 447 N·m | 335 N·m | 252 N·m |
| M4 × 0.7 | 10.9 | 4 N·m | 3 N·m | 2 N·m |
| M5 × 0.8 | 10.9 | 8 N·m | 6 N·m | 5 N·m |
| M6 × 1.0 | 10.9 | 15 N·m | 11 N·m | 8 N·m |
| M8 × 1.25 | 10.9 | 36 N·m | 27 N·m | 20 N·m |
| M10 × 1.5 | 10.9 | 75 N·m | 56 N·m | 42 N·m |
| M12 × 1.75 | 10.9 | 130 N·m | 98 N·m | 73 N·m |
| M14 × 2.0 | 10.9 | 207 N·m | 155 N·m | 116 N·m |
| M16 × 2.0 | 10.9 | 321 N·m | 241 N·m | 181 N·m |
| M20 × 2.5 | 10.9 | 628 N·m | 471 N·m | 353 N·m |
| M4 × 0.7 | 12.9 | 5 N·m | 4 N·m | 3 N·m |
| M5 × 0.8 | 12.9 | 10 N·m | 7 N·m | 5 N·m |
| M6 × 1.0 | 12.9 | 17 N·m | 13 N·m | 10 N·m |
| M8 × 1.25 | 12.9 | 43 N·m | 32 N·m | 24 N·m |
| M10 × 1.5 | 12.9 | 88 N·m | 66 N·m | 49 N·m |
| M12 × 1.75 | 12.9 | 152 N·m | 114 N·m | 86 N·m |
| M14 × 2.0 | 12.9 | 243 N·m | 182 N·m | 136 N·m |
| M16 × 2.0 | 12.9 | 376 N·m | 282 N·m | 212 N·m |
| M20 × 2.5 | 12.9 | 736 N·m | 552 N·m | 414 N·m |
About the values. Torque is the indirect way to achieve a target bolt tension. The K-factor depends on thread finish, lubrication, and washer condition — values shown are typical, not absolute. For critical joints, use a tension-indicating method (direct-tension washer, strain gauge, or yield-point method) rather than torque alone.
Common applications
| Use case | Typical bolt | Note |
|---|---|---|
| Automotive lug nut | 1/2-20 or M14 | Always check vehicle manufacturer spec — varies 80–150 ft·lbf |
| Engine cylinder head | M10–M12 stretch bolt | Torque-to-yield (TTY); use the angle method, not just torque |
| Bicycle stem bolt | M5 or M6 | Typically 5–8 N·m. Over-torque cracks carbon parts |
| Bicycle pedal | 9/16″ or M14 | 30–35 ft·lbf typical |
| Furniture assembly bolt | M6 or M8 | Hand-tight + 1/4 turn; particleboard threads strip easily |
| Structural steel connection | 3/4-10 A325 | Slip-critical: turn-of-nut or DTI washer, not torque |
Common pitfalls
- Lubrication changes torque ~30%. A dry-spec bolt over-torqued because someone added oil will snap. A lubed bolt under-torqued because spec was for lubed will loosen.
- Used bolts have different friction. Re-used fasteners may need different torque. Critical joints should use new fasteners.
- Galvanized and stainless are different. Galvanized increases friction (~20%); stainless tends to gall and seize. Use anti-seize on stainless.
- Torque ≠ tension. Even with perfect technique, torque-to-tension correlation has ±25% scatter. For mission-critical joints, measure tension directly.
- Bolt grade matters more than size. A Grade 8 1/4″ bolt holds more than a Grade 2 3/8″ bolt. Check the head markings.
Common questions
Why does my torque spec say 'lubricated' or 'dry'?
About 90% of applied torque is consumed by friction (between threads and under the bolt head); only ~10% actually produces clamping force. Lubrication reduces friction, so the same torque produces more preload. A dry torque spec applied to a lubricated bolt can overstretch it by 30-50% and break it. Always match your bolt condition to the spec.
What torque should I use if I don't have a spec?
For grade 5 (or class 8.8) bolts in steel, a reasonable rule of thumb is T = 0.2 × D × proof-load-force, with T in lb·ft, D in inches, and force in lbf. For a 1/2-13 grade 5 bolt (D = 0.5 in, proof load ~12,030 lbf), T ≈ 0.2 × 0.5 × 12,030 / 12 = 100 lb·ft. Always cross-check against a published table; rules of thumb are starting points, not specs.
Can I reuse a bolt that's been torqued before?
It depends on whether it was torqued into the yield range (most aerospace and engine bolts) or below yield (most general fasteners). Yield-tightened bolts plastically deform and should never be reused. Standard fasteners torqued below their proof load can usually be reused 2-3 times — but inspect for thread damage, stretching, or corrosion before reuse.
What's the difference between proof load and yield strength?
Proof load is the highest load a bolt can take without permanent deformation; yield strength is the load at which deformation starts. Proof load is typically set at 90% of yield to give a safety margin. Bolt grades (5, 8, 10.9, 12.9) are categorized by proof load, not yield, because proof is what matters for repeated use.
Why are anti-seize compounds problematic for torque specs?
Most anti-seize compounds (copper, nickel, moly-disulfide) reduce friction so much that standard torque specs over-tighten the bolt. If you must use anti-seize, reduce the torque by 20-30% or use a torque-angle method instead. Some manufacturers explicitly forbid anti-seize on critical bolts because of this.
What is the tensile strength of an SAE Grade 5 bolt?
An SAE Grade 5 medium-carbon steel bolt (1/4 to 1 inch) has a proof load of about 85,000 PSI and a minimum ultimate tensile strength of about 120,000 PSI.
What does '8.8' stamped on a metric bolt head mean?
An 8.8 marking means a medium-carbon steel metric bolt with roughly 800 MPa ultimate tensile strength (and about 640 MPa yield) — comparable to an SAE Grade 5.
Sources
- Methodology: ISO 16047 — Fasteners, torque/clamp force testing.
- Imperial values: SAE J429 (bolt grades) cross-referenced with Machinery's Handbook 31st ed.
- Metric values: ISO 898-1 (mechanical properties) cross-referenced with Machinery's Handbook.
- K-factor formula: T = K × D × P, where T = torque, K = friction factor, D = nominal diameter, P = clamp load (typically 75% of proof load).
Disclaimer. Torque values are guidelines, not specifications. For any joint where failure has consequences (structural, automotive, machinery), use the manufacturer's torque spec, not a general chart.