M2.5 Bolt Torque
An M2.5 8.8 bolt with a coarse M2.5×0.45 thread needs about 0.84 N·m (0.62 ft·lb) when dry and 0.63 N·m (0.46 ft·lb) when oiled, tightened to 70% of yield (clamp force 1.52 kN).
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 0.57 kN128 lbf | 0.31 N·m0.23 ft·lb | 0.24 N·m0.17 ft·lb | 0.16 N·m0.12 ft·lb |
| 4.8 | 0.76 kN171 lbf | 0.42 N·m0.31 ft·lb | 0.31 N·m0.23 ft·lb | 0.21 N·m0.16 ft·lb |
| 5.6 | 0.71 kN160 lbf | 0.39 N·m0.29 ft·lb | 0.29 N·m0.22 ft·lb | 0.20 N·m0.15 ft·lb |
| 5.8 | 0.95 kN213 lbf | 0.52 N·m0.39 ft·lb | 0.39 N·m0.29 ft·lb | 0.26 N·m0.19 ft·lb |
| 6.8 | 1.14 kN256 lbf | 0.63 N·m0.46 ft·lb | 0.47 N·m0.35 ft·lb | 0.32 N·m0.23 ft·lb |
| 8.8 | 1.52 kN342 lbf | 0.84 N·m0.62 ft·lb | 0.63 N·m0.46 ft·lb | 0.42 N·m0.31 ft·lb |
| 9.8 | 1.71 kN384 lbf | 0.94 N·m0.69 ft·lb | 0.71 N·m0.52 ft·lb | 0.48 N·m0.35 ft·lb |
| 10.9 | 2.14 kN480 lbf | 1.18 N·m0.87 ft·lb | 0.88 N·m0.65 ft·lb | 0.59 N·m0.44 ft·lb |
| 12.9 | 2.56 kN576 lbf | 1.41 N·m1.04 ft·lb | 1.06 N·m0.78 ft·lb | 0.71 N·m0.53 ft·lb |
| A2-70 | 1.07 kN240 lbf | 0.59 N·m0.43 ft·lb | 0.44 N·m0.33 ft·lb | 0.30 N·m0.22 ft·lb |
| A4-70 | 1.07 kN240 lbf | 0.59 N·m0.43 ft·lb | 0.44 N·m0.33 ft·lb | 0.30 N·m0.22 ft·lb |
| A4-80 | 1.42 kN320 lbf | 0.78 N·m0.58 ft·lb | 0.59 N·m0.44 ft·lb | 0.40 N·m0.29 ft·lb |
| Grade | Clamp forcepreload | Dryμ 0.15 | Oiledμ 0.11 | PTFE / moly pasteμ 0.06 |
|---|---|---|---|---|
| 4.6 | 0.62 kN140 lbf | 0.34 N·m0.25 ft·lb | 0.25 N·m0.18 ft·lb | 0.16 N·m0.12 ft·lb |
| 4.8 | 0.83 kN187 lbf | 0.45 N·m0.33 ft·lb | 0.33 N·m0.25 ft·lb | 0.22 N·m0.16 ft·lb |
| 5.6 | 0.78 kN175 lbf | 0.42 N·m0.31 ft·lb | 0.31 N·m0.23 ft·lb | 0.21 N·m0.15 ft·lb |
| 5.8 | 1.04 kN233 lbf | 0.56 N·m0.41 ft·lb | 0.42 N·m0.31 ft·lb | 0.27 N·m0.20 ft·lb |
| 6.8 | 1.24 kN280 lbf | 0.67 N·m0.50 ft·lb | 0.50 N·m0.37 ft·lb | 0.33 N·m0.24 ft·lb |
| 8.8 | 1.66 kN373 lbf | 0.90 N·m0.66 ft·lb | 0.67 N·m0.49 ft·lb | 0.44 N·m0.32 ft·lb |
| 9.8 | 1.87 kN420 lbf | 1.01 N·m0.74 ft·lb | 0.75 N·m0.55 ft·lb | 0.49 N·m0.36 ft·lb |
| 10.9 | 2.33 kN525 lbf | 1.26 N·m0.93 ft·lb | 0.94 N·m0.69 ft·lb | 0.62 N·m0.46 ft·lb |
| 12.9 | 2.80 kN630 lbf | 1.51 N·m1.11 ft·lb | 1.13 N·m0.83 ft·lb | 0.74 N·m0.55 ft·lb |
| A2-70 | 1.17 kN262 lbf | 0.63 N·m0.46 ft·lb | 0.47 N·m0.35 ft·lb | 0.31 N·m0.23 ft·lb |
| A4-70 | 1.17 kN262 lbf | 0.63 N·m0.46 ft·lb | 0.47 N·m0.35 ft·lb | 0.31 N·m0.23 ft·lb |
| A4-80 | 1.56 kN350 lbf | 0.84 N·m0.62 ft·lb | 0.63 N·m0.46 ft·lb | 0.41 N·m0.30 ft·lb |
Torque for M2.5 hex head bolts and nuts, standard ISO/ASME heads on steel with a 2.9 mm clearance hole. Friction μ applies to both the threads and the bearing face. Always follow the manufacturer's value where one exists.
M2.5 thread and dimensions
- Coarse thread
- M2.5×0.45 — pitch 0.45 mm
- Fine thread
- M2.5×0.35 — pitch 0.35 mm
- Tensile stress area Aₛ
- 3.39 mm² (coarse), 3.70 mm² (fine)
- Pitch diameter d₂
- 2.208 mm
- Tap drill
- 2.05 mm (coarse), 2.15 mm (fine)
- Wrench size (hex head)
- 5 mm
- Clearance hole
- 2.9 mm
How the M2.5 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 × 3.39 mm² = 1.52 kN
T = F × (0.16·P + 0.58·μ·d₂ + μ·Dₖₘ/2)
T = 1.52 kN × (0.16·0.45 + 0.58·0.15·2.21 + 0.15·3.95/2) mm = 0.84 N·m
Here d₂ is the pitch diameter and Dₖₘ the effective bearing diameter of the head (3.95 mm). Change the grade, lubrication or preload in the calculator below.
Frequently asked questions
What is the torque for an M2.5 8.8 bolt?
About 0.84 N·m (0.62 ft·lb) with dry threads, 0.63 N·m (0.46 ft·lb) with oiled threads and 0.42 N·m (0.31 ft·lb) with PTFE or moly paste, for a coarse M2.5×0.45 thread tightened to 70% of yield. The resulting clamp force is 1.52 kN.
What is the torque for an M2.5 10.9 bolt?
About 1.18 N·m (0.87 ft·lb) with dry threads, 0.88 N·m (0.65 ft·lb) with oiled threads and 0.59 N·m (0.44 ft·lb) with PTFE or moly paste, for a coarse M2.5×0.45 thread tightened to 70% of yield. The resulting clamp force is 2.14 kN.
What size wrench fits an M2.5 bolt?
A standard M2.5 hex head bolt or nut takes a 5 mm wrench or socket.
What drill size do I need to tap M2.5?
Use a 2.05 mm drill for M2.5×0.45 and 2.15 mm for M2.5×0.35.