Fasteners
Bolt Torque Chart
General torque values calculated from proof load and thread stress area — with separate columns for dry, plated and lubricated, because that single choice moves the number by a quarter.
A dry 1/2-13 Grade 5 takes 75 lb-ft. Its metric counterpart, M12×1.75 class 8.8, takes 88 N·m dry — but only 66 N·m once the threads are oiled. Using the dry figure on a lubricated fastener over-tightens it by about a third.
| Units | ||||||
|---|---|---|---|---|---|---|
| 1/4-20 | Grade 2 | 5.0 | 6.0 | 4.0 | lb-ft | |
| 1/4-20 | Grade 5 | 8.0 | 9.0 | 6.0 | lb-ft | |
| 1/4-20 | Grade 8 | 12.0 | 13.0 | 9.0 | lb-ft | |
| 5/16-18 | Grade 2 | 11.0 | 12.0 | 8.0 | lb-ft | |
| 5/16-18 | Grade 5 | 17.0 | 19.0 | 13.0 | lb-ft | |
| 5/16-18 | Grade 8 | 25.0 | 27.0 | 18.0 | lb-ft | |
| 3/8-16 | Grade 2 | 20.0 | 22.0 | 15.0 | lb-ft | |
| 3/8-16 | Grade 5 | 31.0 | 34.0 | 23.0 | lb-ft | |
| 3/8-16 | Grade 8 | 44.0 | 48.0 | 33.0 | lb-ft | |
| 7/16-14 | Grade 2 | 32.0 | 35.0 | 24.0 | lb-ft | |
| 7/16-14 | Grade 5 | 49.0 | 54.0 | 37.0 | lb-ft | |
| 7/16-14 | Grade 8 | 70.0 | 77.0 | 52.0 | lb-ft | |
| 1/2-13 | Grade 2 | 49.0 | 54.0 | 37.0 | lb-ft | |
| 1/2-13 | Grade 5 | 75.0 | 83.0 | 57.0 | lb-ft | |
| 1/2-13 | Grade 8 | 106.0 | 117.0 | 80.0 | lb-ft | |
| 9/16-12 | Grade 2 | 70.0 | 77.0 | 53.0 | lb-ft | |
| 9/16-12 | Grade 5 | 109.0 | 120.0 | 82.0 | lb-ft | |
| 9/16-12 | Grade 8 | 154.0 | 169.0 | 115.0 | lb-ft | |
| 5/8-11 | Grade 2 | 97.0 | 107.0 | 73.0 | lb-ft | |
| 5/8-11 | Grade 5 | 150.0 | 165.0 | 113.0 | lb-ft | |
| 5/8-11 | Grade 8 | 212.0 | 233.0 | 159.0 | lb-ft | |
| 3/4-10 | Grade 2 | 172.0 | 190.0 | 129.0 | lb-ft | |
| 3/4-10 | Grade 5 | 267.0 | 293.0 | 200.0 | lb-ft | |
| 3/4-10 | Grade 8 | 376.0 | 414.0 | 282.0 | lb-ft | |
| 7/8-9 | Grade 2 | 167.0 | 183.0 | 125.0 | lb-ft | |
| 7/8-9 | Grade 5 | 429.0 | 472.0 | 322.0 | lb-ft | |
| 7/8-9 | Grade 8 | 606.0 | 667.0 | 455.0 | lb-ft | |
| 1-8 | Grade 2 | 250.0 | 275.0 | 187.0 | lb-ft | |
| 1-8 | Grade 5 | 644.0 | 708.0 | 483.0 | lb-ft | |
| 1-8 | Grade 8 | 909.0 | 999.0 | 681.0 | lb-ft | |
| 1-1/8-7 | Grade 2 | 354.0 | 390.0 | 266.0 | lb-ft | |
| 1-1/8-7 | Grade 5 | 794.0 | 874.0 | 596.0 | lb-ft | |
| 1-1/8-7 | Grade 8 | 1288.0 | 1417.0 | 966.0 | lb-ft | |
| 1-1/4-7 | Grade 2 | 500.0 | 550.0 | 375.0 | lb-ft | |
| 1-1/4-7 | Grade 5 | 1121.0 | 1233.0 | 840.0 | lb-ft | |
| 1-1/4-7 | Grade 8 | 1817.0 | 1999.0 | 1363.0 | lb-ft | |
| M5×0.8 | Class 8.8 | 6.2 | 6.8 | 4.6 | N·m | |
| M5×0.8 | Class 10.9 | 8.8 | 9.7 | 6.6 | N·m | |
| M5×0.8 | Class 12.9 | 10.3 | 11.3 | 7.7 | N·m | |
| M6×1 | Class 8.8 | 10.5 | 11.6 | 7.9 | N·m | |
| M6×1 | Class 10.9 | 15.0 | 16.5 | 11.3 | N·m | |
| M6×1 | Class 12.9 | 17.6 | 19.3 | 13.2 | N·m | |
| M8×1.25 | Class 8.8 | 25.5 | 28.0 | 19.1 | N·m | |
| M8×1.25 | Class 10.9 | 36.5 | 40.1 | 27.3 | N·m | |
| M8×1.25 | Class 12.9 | 42.6 | 46.9 | 32.0 | N·m | |
| M10×1.5 | Class 8.8 | 50.5 | 55.5 | 37.8 | N·m | |
| M10×1.5 | Class 10.9 | 72.2 | 79.4 | 54.1 | N·m | |
| M10×1.5 | Class 12.9 | 84.4 | 92.8 | 63.3 | N·m | |
| M12×1.75 | Class 8.8 | 88.0 | 96.8 | 66.0 | N·m | |
| M12×1.75 | Class 10.9 | 125.9 | 138.5 | 94.4 | N·m | |
| M12×1.75 | Class 12.9 | 147.1 | 161.8 | 110.3 | N·m | |
| M14×2 | Class 8.8 | 140.6 | 154.7 | 105.5 | N·m | |
| M14×2 | Class 10.9 | 201.2 | 221.3 | 150.9 | N·m | |
| M14×2 | Class 12.9 | 235.2 | 258.7 | 176.4 | N·m | |
| M16×2 | Class 8.8 | 218.1 | 239.9 | 163.6 | N·m | |
| M16×2 | Class 10.9 | 312.1 | 343.3 | 234.1 | N·m | |
| M16×2 | Class 12.9 | 364.7 | 401.2 | 273.5 | N·m | |
| M20×2.5 | Class 8.8 | 425.9 | 468.5 | 319.5 | N·m | |
| M20×2.5 | Class 10.9 | 609.5 | 670.5 | 457.2 | N·m | |
| M20×2.5 | Class 12.9 | 712.4 | 783.6 | 534.3 | N·m | |
| M24×3 | Class 8.8 | 736.0 | 809.6 | 552.0 | N·m | |
| M24×3 | Class 10.9 | 1053.3 | 1158.6 | 790.0 | N·m | |
| M24×3 | Class 12.9 | 1230.9 | 1354.0 | 923.2 | N·m |
Inch rows are lb-ft, metric rows are N·m. Bars scale with bolt diameter.
Where the numbers come from
F = 0.75 × Sp × At preload, at 75% of proof load T = K × D × F K = 0.20 dry, 0.22 zinc, 0.15 lubricated
Torque is a proxy. What actually holds a joint together is preload — the tension in the bolt — and torque is just the most practical way to approximate it. Most of the torque you apply is spent overcoming friction, not stretching the bolt, which is why the friction coefficient matters as much as the bolt grade.
Proof load, not yield strength
These values are built on proof stress — the stress a bolt takes without measurable permanent set — rather than yield strength. Building the same table on yield overstates torque by roughly 8% in inch sizes and up to 20% in metric. On a torque chart that is a safety error, not a rounding difference.
Lubrication changes the answer, not just the feel
Anti-seize, oil, or fresh zinc plating all lower friction. Lower friction means more of your torque becomes tension, so the same reading produces a tighter bolt. Applying a dry-spec torque to a lubricated fastener is one of the most common ways to snap it.
If the spec you are working to does not say which condition it assumes, assume dry — and if you have lubricated the threads, reduce by about 25%.
Lug nuts
Wheel torque is genuinely vehicle-specific, but it tracks thread size closely enough to give a sanity-check range. Use these to catch a gross error, not as a substitute for the figure in your owner's manual.
| Thread | Typical N·m | Typical lb-ft | Commonly seen on |
|---|---|---|---|
| M12×1.5 | 110–120 | 80–90 | Many compact and mid-size cars |
| M12×1.25 | 110–120 | 80–90 | Some Japanese makes |
| M14×1.5 | 140–160 | 100–120 | Larger cars, many SUVs, EVs |
| M14×1.25 | 140–160 | 100–120 | Some European makes |
| 1/2-20 | 115–135 | 85–100 | Older domestic cars, trailers |
| 9/16-18 | 160–190 | 120–140 | Half-ton trucks |
Tighten in a star pattern, in two or three passes, with the wheel on the ground for the final pass. Never use an impact wrench for the last step — and re-check after the first 50 miles on a wheel that has just been off.
Spark plugs
Plug torque depends on the seat type, not just thread size. Gasket plugs crush a washer; taper-seat plugs seal on a cone and need far less rotation past contact.
| Thread | Seat | N·m | lb-ft | If you have no wrench |
|---|---|---|---|---|
| M10 | Gasket | 10–15 | 7–11 | About 1/2 turn past finger-tight |
| M12 | Gasket | 15–25 | 11–18 | About 1/2 turn past finger-tight |
| M14 | Gasket | 25–30 | 18–22 | About 1/2 turn past finger-tight |
| M18 | Gasket | 35–45 | 26–33 | About 1/4 turn past finger-tight |
| M14 | Taper seat | 20–30 | 15–22 | About 1/16 turn past finger-tight |
| M18 | Taper seat | 20–30 | 15–22 | About 1/16 turn past finger-tight |
Aluminum heads are unforgiving here — stripping a plug hole is an expensive repair, and an under-torqued plug runs hot because it cannot shed heat into the head.
Data source and method
- Strength
- SAE J429 proof stress (Grade 2 / 5 / 8) and ISO 898-1 proof stress (class 8.8 / 10.9 / 12.9).
- Stress area
- Computed:
At = 0.7854 × (D − 0.9743/n)²inch,As = 0.7854 × (D − 0.9382 × P)²metric. - Torque
T = K × D × FwithF = 0.75 × Sp × At. K is a friction coefficient, not a constant — it shifts with plating, lubricant, surface finish and reuse.- Verification
- Checked against published values: 1/2-13 Grade 5 = 75 lb-ft, Grade 8 = 106 lb-ft, 3/8-16 Grade 5 = 31 lb-ft, M10×1.5 class 8.8 = 50.5 N·m, M8×1.25 class 10.9 = 36.5 N·m. All land inside the commonly published ranges.
- Deliberately absent
- Vehicle-specific and equipment-specific torque specifications. See the notice above.
Related charts
- Socket size chart — which socket fits the fastener
- Thread size chart — the stress areas behind these numbers