- T
- Tightening torque: what you set on the torque wrench
- F
- Clamp force (preload): how hard the bolt squeezes the joint, here 75% of its proof load
- d
- Bolt size: the thread's nominal diameter (M10 = 10 mm, 1/2 in)
Metric bolts, dry threads
| Bolt | 8.8 (N·m) | 10.9 (N·m) | 12.9 (N·m) | 8.8 (lbf·ft) | 10.9 (lbf·ft) | 12.9 (lbf·ft) |
|---|---|---|---|---|---|---|
| M3 | 1.31 | 1.88 | 2.2 | 0.968 | 1.39 | 1.62 |
| M3.5 | 2.06 | 2.95 | 3.45 | 1.52 | 2.18 | 2.54 |
| M4 | 3.05 | 4.37 | 5.11 | 2.25 | 3.22 | 3.77 |
| M5 | 6.17 | 8.83 | 10.3 | 4.55 | 6.51 | 7.61 |
| M6 | 10.5 | 15 | 17.6 | 7.75 | 11.1 | 13 |
| M8 | 25.5 | 36.5 | 42.6 | 18.8 | 26.9 | 31.4 |
| M10 | 50.5 | 72.2 | 84.4 | 37.2 | 53.2 | 62.2 |
| M12 | 88 | 126 | 147 | 64.9 | 92.9 | 109 |
| M14 | 141 | 201 | 235 | 104 | 148 | 173 |
| M16 | 218 | 312 | 365 | 161 | 230 | 269 |
| M18 | 312 | 431 | 504 | 230 | 318 | 372 |
| M20 | 441 | 610 | 712 | 325 | 450 | 525 |
| M22 | 601 | 831 | 971 | 443 | 613 | 716 |
| M24 | 761 | 1050 | 1230 | 562 | 777 | 908 |
| M27 | 1120 | 1540 | 1800 | 823 | 1140 | 1330 |
| M30 | 1510 | 2090 | 2450 | 1120 | 1540 | 1800 |
| M33 | 2060 | 2850 | 3330 | 1520 | 2100 | 2460 |
| M36 | 2650 | 3660 | 4280 | 1950 | 2700 | 3160 |
Dry: plain or zinc-plated steel as supplied (nut factor K 0.2). Coarse thread.
Metric bolts, lightly oiled
| Bolt | 8.8 (N·m) | 10.9 (N·m) | 12.9 (N·m) | 8.8 (lbf·ft) | 10.9 (lbf·ft) | 12.9 (lbf·ft) |
|---|---|---|---|---|---|---|
| M3 | 0.985 | 1.41 | 1.65 | 0.726 | 1.04 | 1.21 |
| M3.5 | 1.55 | 2.21 | 2.59 | 1.14 | 1.63 | 1.91 |
| M4 | 2.29 | 3.28 | 3.83 | 1.69 | 2.42 | 2.83 |
| M5 | 4.63 | 6.62 | 7.74 | 3.41 | 4.88 | 5.71 |
| M6 | 7.88 | 11.3 | 13.2 | 5.81 | 8.32 | 9.72 |
| M8 | 19.1 | 27.3 | 32 | 14.1 | 20.2 | 23.6 |
| M10 | 37.8 | 54.1 | 63.3 | 27.9 | 39.9 | 46.7 |
| M12 | 66 | 94.4 | 110 | 48.7 | 69.6 | 81.4 |
| M14 | 105 | 151 | 176 | 77.8 | 111 | 130 |
| M16 | 164 | 234 | 274 | 121 | 173 | 202 |
| M18 | 234 | 323 | 378 | 172 | 239 | 279 |
| M20 | 330 | 457 | 534 | 244 | 337 | 394 |
| M22 | 451 | 623 | 728 | 332 | 460 | 537 |
| M24 | 571 | 790 | 923 | 421 | 583 | 681 |
| M27 | 837 | 1160 | 1350 | 618 | 854 | 998 |
| M30 | 1140 | 1570 | 1840 | 837 | 1160 | 1350 |
| M33 | 1540 | 2140 | 2500 | 1140 | 1580 | 1840 |
| M36 | 1980 | 2750 | 3210 | 1460 | 2020 | 2370 |
Lightly oiled threads (nut factor K 0.15) need about 25% less torque for the same clamp force. With anti-seize or moly paste (K 0.12), use about 40% less than dry: the bolt torque calculator works it out.
UNC bolts, dry threads
| Bolt | Grade 2 (lbf·ft) | Grade 5 (lbf·ft) | Grade 8 (lbf·ft) | Grade 2 (N·m) | Grade 5 (N·m) | Grade 8 (N·m) |
|---|---|---|---|---|---|---|
| 1/4-20 | 5.47 | 8.45 | 11.9 | 7.42 | 11.5 | 16.2 |
| 5/16-18 | 11.3 | 17.4 | 24.6 | 15.3 | 23.6 | 33.3 |
| 3/8-16 | 20 | 30.9 | 43.6 | 27.1 | 41.9 | 59.1 |
| 7/16-14 | 32 | 49.4 | 69.8 | 43.4 | 67 | 94.6 |
| 1/2-13 | 48.8 | 75.4 | 106 | 66.1 | 102 | 144 |
| 9/16-12 | 70.4 | 109 | 154 | 95.4 | 147 | 208 |
| 5/8-11 | 97.1 | 150 | 212 | 132 | 203 | 287 |
| 3/4-10 | 172 | 267 | 376 | 234 | 361 | 510 |
| 7/8-9 | 167 | 429 | 606 | 226 | 582 | 822 |
| 1-8 | 250 | 644 | 909 | 339 | 873 | 1230 |
Dry: plain or zinc-plated steel as supplied (nut factor K 0.2). UNC is the coarse inch thread: 1/2-13 is 1/2 inch across with 13 threads per inch.
UNC bolts, lightly oiled
| Bolt | Grade 2 (lbf·ft) | Grade 5 (lbf·ft) | Grade 8 (lbf·ft) | Grade 2 (N·m) | Grade 5 (N·m) | Grade 8 (N·m) |
|---|---|---|---|---|---|---|
| 1/4-20 | 4.1 | 6.34 | 8.95 | 5.56 | 8.6 | 12.1 |
| 5/16-18 | 8.45 | 13.1 | 18.4 | 11.5 | 17.7 | 25 |
| 3/8-16 | 15 | 23.2 | 32.7 | 20.3 | 31.4 | 44.3 |
| 7/16-14 | 24 | 37.1 | 52.3 | 32.5 | 50.3 | 70.9 |
| 1/2-13 | 36.6 | 56.5 | 79.8 | 49.6 | 76.7 | 108 |
| 9/16-12 | 52.8 | 81.6 | 115 | 71.5 | 111 | 156 |
| 5/8-11 | 72.8 | 113 | 159 | 98.7 | 153 | 215 |
| 3/4-10 | 129 | 200 | 282 | 175 | 271 | 383 |
| 7/8-9 | 125 | 322 | 455 | 169 | 437 | 616 |
| 1-8 | 187 | 483 | 681 | 254 | 654 | 924 |
Lightly oiled threads (nut factor K 0.15) need about 25% less torque for the same clamp force. With anti-seize or moly paste (K 0.12), use about 40% less than dry: the bolt torque calculator works it out.
UNF bolts, dry threads
| Bolt | Grade 2 (lbf·ft) | Grade 5 (lbf·ft) | Grade 8 (lbf·ft) | Grade 2 (N·m) | Grade 5 (N·m) | Grade 8 (N·m) |
|---|---|---|---|---|---|---|
| 1/4-28 | 6.25 | 9.66 | 13.6 | 8.48 | 13.1 | 18.5 |
| 5/16-24 | 12.5 | 19.3 | 27.2 | 16.9 | 26.1 | 36.9 |
| 3/8-24 | 22.6 | 35 | 49.4 | 30.7 | 47.4 | 67 |
| 7/16-20 | 35.7 | 55.2 | 77.9 | 48.4 | 74.8 | 106 |
| 1/2-20 | 55 | 85 | 120 | 74.5 | 115 | 163 |
| 9/16-18 | 78.5 | 121 | 171 | 106 | 164 | 232 |
| 5/8-18 | 110 | 170 | 240 | 149 | 230 | 325 |
| 3/4-16 | 192 | 297 | 420 | 261 | 403 | 569 |
| 7/8-14 | 184 | 474 | 669 | 249 | 642 | 907 |
| 1-12 | 274 | 704 | 995 | 371 | 955 | 1350 |
Dry: plain or zinc-plated steel as supplied (nut factor K 0.2). UNF is the fine inch thread.
UNF bolts, lightly oiled
| Bolt | Grade 2 (lbf·ft) | Grade 5 (lbf·ft) | Grade 8 (lbf·ft) | Grade 2 (N·m) | Grade 5 (N·m) | Grade 8 (N·m) |
|---|---|---|---|---|---|---|
| 1/4-28 | 4.69 | 7.25 | 10.2 | 6.36 | 9.82 | 13.9 |
| 5/16-24 | 9.36 | 14.5 | 20.4 | 12.7 | 19.6 | 27.7 |
| 3/8-24 | 17 | 26.2 | 37.1 | 23 | 35.6 | 50.2 |
| 7/16-20 | 26.8 | 41.4 | 58.4 | 36.3 | 56.1 | 79.2 |
| 1/2-20 | 41.2 | 63.7 | 90 | 55.9 | 86.4 | 122 |
| 9/16-18 | 58.9 | 91 | 128 | 79.8 | 123 | 174 |
| 5/8-18 | 82.5 | 127 | 180 | 112 | 173 | 244 |
| 3/4-16 | 144 | 223 | 315 | 196 | 302 | 427 |
| 7/8-14 | 138 | 355 | 502 | 187 | 482 | 680 |
| 1-12 | 205 | 528 | 746 | 278 | 716 | 1010 |
Lightly oiled threads (nut factor K 0.15) need about 25% less torque for the same clamp force. With anti-seize or moly paste (K 0.12), use about 40% less than dry: the bolt torque calculator works it out.
About this chart
How tight to do up a bolt with no torque figure from the maker: the torque that clamps the joint at 75% of the bolt's proof load, the usual target for bolts that may be taken apart again. Choose the thread and whether the threads are dry or oiled above the chart.
The grade is stamped on the head: 8.8, 10.9 or 12.9 on metric bolts; on inch bolts, 3 radial lines for Grade 5 and 6 for Grade 8 (none for Grade 2). For other grades, stainless bolts or a different clamp force, use the bolt torque calculator.
How it's worked out:
- Proof load = proof stress × tensile stress area. Proof stress: 8.8 580 MPa (600 MPa over M16), 10.9 830 MPa, 12.9 970 MPa (ISO 898-1); Grade 2 55 ksi (33 ksi over 3/4 in), Grade 5 85 ksi (74 ksi over 1 in), Grade 8 120 ksi (SAE J429)
- Clamp force F = 75% of the proof load
- Torque T = K × F × d, with the nut factor K 0.2 dry and 0.15 lightly oiled
A guide based on typical friction. Always use the maker's figure where there is one (engines, wheels, structural steelwork), and remember that friction varies, so a torque wrench sets clamp force to about ±25%. Torques are to 3 significant figures, like the calculator.
Last checked 31 October 2026 · Last rev. 31 October 2026 · 4cdd