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M4 bolt size
7 mm wrench
across-flats spanner / socket size for M4
M4 bolt — small appliances, brackets and covers.
Full specification
| System | Metric coarse |
| Nominal diameter | 4 mm |
| Thread pitch | 0.7 mm |
| Wrench / spanner (across flats) | 7 mm |
| Tap drill | 3.3 mm |
| Clearance hole | 4.5 mm |
| Common grade / class | 8.8 |
| Typical torque | 3 Nm (2.2 ft·lb) |
| Closest other-system size | ~#8 imperial |
🔧 Torque unit converter
Pre-filled with the typical torque for M4 (8.8, dry). Edit any field to convert.
⚠️ Torque values here are general references for 8.8 on clean, dry threads. Lubrication, coatings, and the joint material change the figure significantly. For structural, automotive, or safety-critical work, always use the torque specified by the manufacturer or engineer.
About M4
M4 bolts are common in small appliances, computer cases and light brackets.
A 3.3 mm tap drill gives the correct 70 percent thread engagement for M4.
Frequently asked questions
- What size wrench or spanner fits M4?
- M4 bolt uses a 7 mm wrench or spanner, measured across the flats of the hex head.
- What is the torque for M4?
- A typical tightening torque for M4 bolt in 8.8 on dry threads is about 3 Nm (2.2 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does M4 use?
- M4 bolt has a thread pitch of 0.7 mm and uses a 3.3 mm tap drill, with a 4.5 mm clearance hole.