M4 Bolt Torque
An M4 8.8 bolt with a coarse M4×0.7 thread needs about 3.29 N·m (2.43 ft·lb) when dry and 2.48 N·m (1.83 ft·lb) when oiled, tightened to 70% of yield (clamp force 3.93 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 1.47 kN332 lbf | 1.23 N·m0.91 ft·lb | 0.93 N·m0.69 ft·lb | 0.63 N·m0.46 ft·lb |
| 4.8 | 1.97 kN442 lbf | 1.64 N·m1.21 ft·lb | 1.24 N·m0.91 ft·lb | 0.84 N·m0.62 ft·lb |
| 5.6 | 1.84 kN414 lbf | 1.54 N·m1.14 ft·lb | 1.16 N·m0.86 ft·lb | 0.78 N·m0.58 ft·lb |
| 5.8 | 2.46 kN553 lbf | 2.06 N·m1.52 ft·lb | 1.55 N·m1.14 ft·lb | 1.04 N·m0.77 ft·lb |
| 6.8 | 2.95 kN663 lbf | 2.47 N·m1.82 ft·lb | 1.86 N·m1.37 ft·lb | 1.25 N·m0.92 ft·lb |
| 8.8 | 3.93 kN884 lbf | 3.29 N·m2.43 ft·lb | 2.48 N·m1.83 ft·lb | 1.67 N·m1.23 ft·lb |
| 9.8 | 4.42 kN995 lbf | 3.70 N·m2.73 ft·lb | 2.79 N·m2.06 ft·lb | 1.88 N·m1.39 ft·lb |
| 10.9 | 5.53 kN1243 lbf | 4.62 N·m3.41 ft·lb | 3.49 N·m2.57 ft·lb | 2.35 N·m1.73 ft·lb |
| 12.9 | 6.64 kN1492 lbf | 5.55 N·m4.09 ft·lb | 4.18 N·m3.09 ft·lb | 2.82 N·m2.08 ft·lb |
| A2-70 | 2.77 kN622 lbf | 2.31 N·m1.71 ft·lb | 1.74 N·m1.29 ft·lb | 1.17 N·m0.87 ft·lb |
| A4-70 | 2.77 kN622 lbf | 2.31 N·m1.71 ft·lb | 1.74 N·m1.29 ft·lb | 1.17 N·m0.87 ft·lb |
| A4-80 | 3.69 kN829 lbf | 3.08 N·m2.27 ft·lb | 2.32 N·m1.71 ft·lb | 1.57 N·m1.15 ft·lb |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 1.65 kN370 lbf | 1.34 N·m0.99 ft·lb | 1.00 N·m0.74 ft·lb | 0.65 N·m0.48 ft·lb |
| 4.8 | 2.19 kN493 lbf | 1.79 N·m1.32 ft·lb | 1.33 N·m0.98 ft·lb | 0.87 N·m0.64 ft·lb |
| 5.6 | 2.06 kN462 lbf | 1.68 N·m1.24 ft·lb | 1.25 N·m0.92 ft·lb | 0.82 N·m0.60 ft·lb |
| 5.8 | 2.74 kN616 lbf | 2.24 N·m1.65 ft·lb | 1.66 N·m1.23 ft·lb | 1.09 N·m0.80 ft·lb |
| 6.8 | 3.29 kN740 lbf | 2.68 N·m1.98 ft·lb | 1.99 N·m1.47 ft·lb | 1.31 N·m0.96 ft·lb |
| 8.8 | 4.39 kN986 lbf | 3.58 N·m2.64 ft·lb | 2.66 N·m1.96 ft·lb | 1.74 N·m1.29 ft·lb |
| 9.8 | 4.94 kN1109 lbf | 4.02 N·m2.97 ft·lb | 2.99 N·m2.21 ft·lb | 1.96 N·m1.45 ft·lb |
| 10.9 | 6.17 kN1387 lbf | 5.03 N·m3.71 ft·lb | 3.74 N·m2.76 ft·lb | 2.45 N·m1.81 ft·lb |
| 12.9 | 7.40 kN1664 lbf | 6.03 N·m4.45 ft·lb | 4.49 N·m3.31 ft·lb | 2.94 N·m2.17 ft·lb |
| A2-70 | 3.08 kN693 lbf | 2.51 N·m1.85 ft·lb | 1.87 N·m1.38 ft·lb | 1.23 N·m0.90 ft·lb |
| A4-70 | 3.08 kN693 lbf | 2.51 N·m1.85 ft·lb | 1.87 N·m1.38 ft·lb | 1.23 N·m0.90 ft·lb |
| A4-80 | 4.11 kN925 lbf | 3.35 N·m2.47 ft·lb | 2.49 N·m1.84 ft·lb | 1.63 N·m1.21 ft·lb |
Torque for M4 hex head bolts and nuts, standard ISO/ASME heads on steel with a 4.5 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
M4 thread and dimensions
- Coarse thread
- M4×0.7 — pitch 0.7 mm
- Fine thread
- M4×0.5 — pitch 0.5 mm
- Tensile stress area Aₛ
- 8.78 mm² (coarse), 9.79 mm² (fine)
- Pitch diameter d₂
- 3.545 mm
- Tap drill
- 3.3 mm (coarse), 3.5 mm (fine)
- Wrench size (hex head)
- 7 mm
- Clearance hole
- 4.5 mm
How the M4 torque is calculated
Preload is 70% of the bolt's yield strength times its tensile stress area. Torque then follows the ISO 16047 / VDI 2230 formula, which splits it into thread pitch, thread friction and friction under the head:
F = 70% × 640 MPa × 8.78 mm² = 3.93 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 3.93 kN × (0.16·0.7 + 0.58·0.15·3.55 + 0.15·5.75/2) mm = 3.29 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (5.75 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for an M4 8.8 bolt?
About 3.29 N·m (2.43 ft·lb) with dry threads, 2.48 N·m (1.83 ft·lb) with oiled threads and 1.67 N·m (1.23 ft·lb) with PTFE or moly paste, for a coarse M4×0.7 thread tightened to 70% of yield. The resulting clamp force is 3.93 kN.
What is the torque for an M4 10.9 bolt?
About 4.62 N·m (3.41 ft·lb) with dry threads, 3.49 N·m (2.57 ft·lb) with oiled threads and 2.35 N·m (1.73 ft·lb) with PTFE or moly paste, for a coarse M4×0.7 thread tightened to 70% of yield. The resulting clamp force is 5.53 kN.
What size wrench fits an M4 bolt?
A standard M4 hex head bolt or nut takes a 7 mm wrench or socket.
What drill size do I need to tap M4?
Use a 3.3 mm drill for M4×0.7 and 3.5 mm for M4×0.5.