Tool
Bolt Torque Calculator
Recommended tightening torque and resulting clamp force for metric (M) and SAE / inch fasteners. Includes tap drill sizes, proof / yield / ultimate loads, and a lubrication-aware T = K·D·F calculation.
System
Recommended torque
25.47 N·m
18.79 lbf·ft · 225.5 lbf·in
T = K · D · F
(0.20 × 8.00 mm × 15921 N)
Clamp force at target preload
15.92 kN
3579 lbf · 1623.5 kgf
75% of proof load (21228 N).
Strength data
- Proof load stress
- 580 MPa
- Yield stress
- 640 MPa
- Ultimate tensile
- 800 MPa
- Stress area
- 36.60 mm²
- Proof load (F)
- 21.23 kN (4772 lbf)
- Yield load
- 23.42 kN
- Ultimate load
- 29.28 kN
Geometry & tap drill
- Nominal diameter
- 8 mm
- Coarse pitch
- 1.25 mm
- Fine pitch
- 1 mm
- Tap drill (75% engagement)
- ⌀ 6.8 mm
Quick torque reference for selected grade & lubrication
All sizes in metric system at Class 8.8 · Dry / as-received · 75% preload.
| Size | Stress area | Clamp force | Torque (N·m) | Torque (lbf·ft) |
|---|---|---|---|---|
| M2 | 2.1 mm² | 0.9 kN | 0.4 | 0.3 |
| M2.5 | 3.4 mm² | 1.5 kN | 0.7 | 0.5 |
| M3 | 5.0 mm² | 2.2 kN | 1.3 | 1.0 |
| M4 | 8.8 mm² | 3.8 kN | 3.1 | 2.3 |
| M5 | 14.2 mm² | 6.2 kN | 6.2 | 4.6 |
| M6 | 20.1 mm² | 8.7 kN | 10.5 | 7.7 |
| M8 | 36.6 mm² | 15.9 kN | 25.5 | 18.8 |
| M10 | 58.0 mm² | 25.2 kN | 50.5 | 37.2 |
| M12 | 84.3 mm² | 36.7 kN | 88.0 | 64.9 |
| M14 | 115.0 mm² | 50.0 kN | 140.1 | 103.3 |
| M16 | 157.0 mm² | 68.3 kN | 218.5 | 161.2 |
| M18 | 192.0 mm² | 83.5 kN | 300.7 | 221.8 |
| M20 | 245.0 mm² | 106.6 kN | 426.3 | 314.4 |
| M22 | 303.0 mm² | 131.8 kN | 579.9 | 427.7 |
| M24 | 353.0 mm² | 153.6 kN | 737.1 | 543.6 |
| M27 | 459.0 mm² | 199.7 kN | 1078.2 | 795.2 |
| M30 | 561.0 mm² | 244.0 kN | 1464.2 | 1079.9 |
| M36 | 817.0 mm² | 355.4 kN | 2558.8 | 1887.3 |
Values are general-purpose engineering estimates based on T = K·D·F. Actual torque depends on joint design, friction, surface finish, gasket relaxation, repeated use, and elasticity of the joint. Always consult the OEM, joint analysis (e.g., VDI 2230), or the controlling spec for safety-critical assemblies.
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