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M8 nut size
13 mm wrench
across-flats spanner / socket size for M8 nut
M8 nut — pairs with M8 bolts.
Full specification
| System | Metric |
| Nominal diameter | 8 mm thread |
| Thread pitch | 1.25 mm |
| Wrench / spanner (across flats) | 13 mm |
| Tap drill | n/a |
| Clearance hole | n/a |
| Common grade / class | matches bolt |
| Typical torque | 25 Nm (18.4 ft·lb) |
| Closest other-system size | ~5/16 in nut |
🔧 Torque unit converter
Pre-filled with the typical torque for M8 nut (matches bolt, dry). Edit any field to convert.
⚠️ Torque values here are general references for matches bolt 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 M8 nut
An M8 hex nut takes a 13 mm wrench, the same as an M8 bolt head.
A flat washer under an M8 nut protects soft surfaces from being chewed up.
Frequently asked questions
- What size wrench or spanner fits M8 nut?
- M8 nut uses a 13 mm wrench or spanner, measured across the flats of the hex head.
- What is the torque for M8 nut?
- A typical tightening torque for M8 nut in matches bolt on dry threads is about 25 Nm (18.4 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does M8 nut use?
- M8 nut has a thread pitch of 1.25 mm and uses a n/a tap drill, with a n/a clearance hole.