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1/4-inch bolt size
7/16 in wrench
across-flats spanner / socket size for 1/4 in
1/4-inch bolt — general hardware and furniture.
Full specification
| System | Imperial UNC |
| Nominal diameter | 1/4 in (6.35 mm) |
| Thread pitch | 20 TPI |
| Wrench / spanner (across flats) | 7/16 in |
| Tap drill | #7 (5.1 mm) |
| Clearance hole | 17/64 in |
| Common grade / class | Grade 5 |
| Typical torque | 15 Nm (11.1 ft·lb) |
| Closest other-system size | ~M6 |
🔧 Torque unit converter
Pre-filled with the typical torque for 1/4 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 1/4 in
The 1/4-20 bolt is the everyday general-purpose American fastener.
1/4-20 takes a 7/16 in wrench — a common surprise for those expecting 1/2 inch.
Frequently asked questions
- What size wrench or spanner fits 1/4 in?
- 1/4-inch bolt uses a 7/16 in wrench or spanner, measured across the flats of the hex head.
- What is the torque for 1/4 in?
- A typical tightening torque for 1/4-inch bolt in Grade 5 on dry threads is about 15 Nm (11.1 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does 1/4 in use?
- 1/4-inch bolt has a thread pitch of 20 TPI and uses a #7 (5.1 mm) tap drill, with a 17/64 in clearance hole.