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1/2-inch bolt size
3/4 in wrench
across-flats spanner / socket size for 1/2 in
1/2-inch bolt — structural and automotive.
Full specification
| System | Imperial UNC |
| Nominal diameter | 1/2 in (12.7 mm) |
| Thread pitch | 13 TPI |
| Wrench / spanner (across flats) | 3/4 in |
| Tap drill | 27/64 in (10.7 mm) |
| Clearance hole | 33/64 in |
| Common grade / class | Grade 5 |
| Typical torque | 102 Nm (75 ft·lb) |
| Closest other-system size | ~M12 |
🔧 Torque unit converter
Pre-filled with the typical torque for 1/2 in (Grade 5, dry). Edit any field to convert.
⚠️ Torque values here are general references for Grade 5 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 1/2 in
1/2-13 is a heavy structural and automotive fastener.
A 27/64 in drill is the textbook tap drill for 1/2-13.
Frequently asked questions
- What size wrench or spanner fits 1/2 in?
- 1/2-inch bolt uses a 3/4 in wrench or spanner, measured across the flats of the hex head.
- What is the torque for 1/2 in?
- A typical tightening torque for 1/2-inch bolt in Grade 5 on dry threads is about 102 Nm (75 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does 1/2 in use?
- 1/2-inch bolt has a thread pitch of 13 TPI and uses a 27/64 in (10.7 mm) tap drill, with a 33/64 in clearance hole.