Bolt torque chart: metric and imperial reference by grade and lubrication.
Reference torque values for metric (M5–M30, ISO 898-1 grades 4.8 / 5.8 / 8.8 / 10.9 / 12.9) and imperial fasteners (1/4"–1", SAE Grade 2 / 5 / 8) at dry and lightly-lubricated conditions. Calculated from T = K × D × F at 75% of yield strength preload. ±25% accuracy band — see notes.
The torque formula
Every value in the tables below is computed from the standard torque-tension equation:
Torque-tension equation
T = K × D × F
- T: tightening torque (N·m for metric, ft-lb for imperial)
- K: nut factor (dimensionless, depends on lubrication)
- D: nominal bolt diameter (m for metric, inches for imperial)
- F: target preload (N or lbf) = 0.75 × yield strength × stress area
K factor by lubrication
| Condition | K factor | Notes |
|---|---|---|
| Dry, as-received steel-on-steel | 0.20 | Default for galvanized or black oxide bolts |
| Light machine oil | 0.16 | Typical for assembly-line use |
| Moly-disulfide grease | 0.13 | Aerospace and high-load applications |
| Anti-seize (graphite/copper) | 0.12 | Stainless on stainless, high-temperature joints |
| Zinc-plated, dry | 0.18 | Most commercial-grade hardware |
| Cadmium-plated, dry | 0.16 | Legacy aerospace, less common in 2026 |
| Stainless on stainless (no anti-seize) | 0.30+ | Galling risk — always use anti-seize |
Metric coarse thread torque (N·m) — DRY, K = 0.20
| Size | Pitch | Stress Area (mm²) | 4.8 | 5.8 | 8.8 | 10.9 | 12.9 |
|---|---|---|---|---|---|---|---|
| M5 | 0.80 | 14.2 | 3.6 | 4.5 | 7.2 | 10.3 | 12.4 |
| M6 | 1.00 | 20.1 | 6.1 | 7.6 | 12.2 | 17.5 | 21.0 |
| M8 | 1.25 | 36.6 | 15.0 | 18.7 | 30.0 | 42.9 | 51.4 |
| M10 | 1.50 | 58.0 | 29.7 | 37.1 | 59.4 | 84.9 | 102 |
| M12 | 1.75 | 84.3 | 51.8 | 64.8 | 104 | 148 | 178 |
| M14 | 2.00 | 115 | 82.4 | 103 | 165 | 236 | 283 |
| M16 | 2.00 | 157 | 128 | 160 | 257 | 367 | 440 |
| M18 | 2.50 | 192 | 177 | 221 | 354 | 506 | 607 |
| M20 | 2.50 | 245 | 251 | 313 | 502 | 717 | 860 |
| M22 | 2.50 | 303 | 341 | 426 | 682 | 974 | 1170 |
| M24 | 3.00 | 353 | 434 | 542 | 868 | 1240 | 1490 |
| M27 | 3.00 | 459 | 635 | 793 | 1268 | 1812 | 2174 |
| M30 | 3.50 | 561 | 862 | 1080 | 1726 | 2466 | 2960 |
Values in N·m. For lubricated condition (K=0.16), multiply by 0.80. For anti-seize (K=0.12), multiply by 0.60.
Metric coarse thread torque (N·m) — LUBRICATED, K = 0.16
| Size | 4.8 | 5.8 | 8.8 | 10.9 | 12.9 |
|---|---|---|---|---|---|
| M5 | 2.9 | 3.6 | 5.8 | 8.2 | 9.9 |
| M6 | 4.9 | 6.1 | 9.8 | 14.0 | 16.8 |
| M8 | 12.0 | 15.0 | 24.0 | 34.3 | 41.1 |
| M10 | 23.8 | 29.7 | 47.5 | 67.9 | 81.6 |
| M12 | 41.4 | 51.8 | 83.2 | 118 | 142 |
| M14 | 65.9 | 82.4 | 132 | 189 | 226 |
| M16 | 102 | 128 | 206 | 294 | 352 |
| M20 | 201 | 250 | 402 | 574 | 688 |
| M24 | 347 | 434 | 694 | 992 | 1192 |
| M30 | 690 | 864 | 1381 | 1973 | 2368 |
Imperial coarse thread torque (ft-lb) — DRY, K = 0.20
| Size | TPI | Grade 2 | Grade 5 | Grade 8 |
|---|---|---|---|---|
| 1/4" | 20 | 5.5 | 9 | 12 |
| 5/16" | 18 | 11 | 18 | 25 |
| 3/8" | 16 | 20 | 30 | 45 |
| 7/16" | 14 | 32 | 50 | 70 |
| 1/2" | 13 | 50 | 80 | 110 |
| 9/16" | 12 | 71 | 110 | 155 |
| 5/8" | 11 | 100 | 155 | 220 |
| 3/4" | 10 | 175 | 270 | 380 |
| 7/8" | 9 | 175 | 430 | 600 |
| 1" | 8 | 260 | 650 | 900 |
Values in ft-lb. Multiply by 1.356 to convert to N·m.
Stainless steel torque (N·m) — A2-70 and A4-80
Stainless steel fasteners have a galling risk that requires anti-seize compound. Values below assume K = 0.18 with anti-seize and 75% yield preload per ISO 3506-1.
| Size | Stress Area (mm²) | A2-70 (yield 450 MPa) | A4-80 (yield 600 MPa) |
|---|---|---|---|
| M5 | 14.2 | 3.6 | 4.8 |
| M6 | 20.1 | 6.1 | 8.1 |
| M8 | 36.6 | 14.8 | 19.8 |
| M10 | 58.0 | 29.4 | 39.2 |
| M12 | 84.3 | 51.2 | 68.3 |
| M14 | 115 | 81.5 | 108.7 |
| M16 | 157 | 127 | 169 |
| M20 | 245 | 248 | 331 |
| M24 | 353 | 429 | 572 |
Notes on accuracy
Torque-to-preload conversion has irreducible noise. Even with calibrated wrenches and identical lubricant, the actual preload achieved at a given torque varies by about ±25% across the sample population. The sources of variation:
- Friction variability. Surface finish, lubricant film thickness, and contact area all vary between fasteners. About 90% of the applied torque overcomes friction; only ~10% generates preload.
- Geometry tolerances. ISO 898-1 thread tolerances allow a ±5% variation in stress area at the pitch diameter.
- Wrench calibration drift. A click-type torque wrench loses calibration ~5–8% per year. A digital wrench is more stable but still requires annual calibration.
- Bolt yield strength scatter. ISO 898-1 specifies minimum yield, not actual. A grade 8.8 bolt may have actual yield 5–15% above 640 MPa.
For critical joints, torque is not enough
Engine head bolts, pressure-vessel flanges, structural-steel high-strength connections, and aerospace primary structure all require torque-angle (TTY) or direct preload measurement (ultrasonic / load cell). Torque-only assembly cannot achieve better than ±25% preload accuracy. Torque-plus-angle reduces this to ±10%. Ultrasonic measurement gets to ±3–5%.
5 common torque mistakes
- Using dry torque on lubricated bolts. Applying a dry-condition torque value to a freshly-oiled bolt over-preloads the joint by ~25%. The bolt yields or the thread strips. Always match the table to the assembly condition.
- Reusing previously-torqued bolts. Grade 10.9 and 12.9 bolts are usually loaded close to yield in service. Reusing them at the same torque accumulates plastic strain. Replace structural bolts after one tightening cycle unless specified as reusable.
- Single-pass tightening. Torquing a flange or head in one pass causes uneven preload — the first bolts compress the gasket and reduce preload on neighboring bolts. Always use a 3-pass torque sequence: 33%, 66%, 100% of final torque, in star or cross pattern.
- Skipping wrench calibration. A click-type wrench can drift 8–10% in a year. Calibrate annually or after any drop, and re-zero between uses.
- Wrong stress-area assumption. Some shop charts use nominal cross-section instead of stress area, overstating torque by ~10%. The values in this chart use ISO 898-1 stress area, which is the standard for grade 8.8 / 10.9 / 12.9 calculation.
Need a specific value not in the chart?
For non-standard pitches (fine thread), custom yield assumptions, or different K factors, the MetricMech Bolt Torque Calculator handles arbitrary inputs and produces an audit-ready PDF with the full T = K × D × F derivation, the chosen preload fraction, and lubrication selection. Useful for FAI submissions where the torque value must be traceable to a documented calculation.
References
- ISO 898-1:2013 — Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and studs with specified property classes — Coarse thread and fine pitch thread
- ISO 3506-1:2020 — Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 1: Bolts, screws and studs with specified grades and property classes
- SAE J429 — Mechanical and Material Requirements for Externally Threaded Fasteners
- Bickford, J.H. (2008) — Introduction to the Design and Behavior of Bolted Joints, 4th Ed.
For interactive computation with custom inputs, see the Bolt Torque Calculator. For press fits and interference joints, see the Press / Interference Fit Calculator.