Hex Key Size Chart (Socket Head Cap Screws)
The hex key (Allen wrench) size for each socket head cap screw, in both inch and metric sizes.
| Inch size | Hex key (in) | Metric size | Hex key (mm) |
|---|---|---|---|
| #4-40 | 3/32 | M3 | 2.5 |
| #6-32 | 7/64 | M4 | 3 |
| #8-32 | 9/64 | M5 | 4 |
| #10-24 | 5/32 | M6 | 5 |
| 1/4-20 | 3/16 | M8 | 6 |
| 5/16-18 | 1/4 | M10 | 8 |
| 3/8-16 | 5/16 | M12 | 10 |
| 1/2-13 | 3/8 | M16 | 14 |
Use the exact key size — a worn or undersized key rounds the socket and strips the screw.
Printable PDF
Download the printer-friendly Hex Key Size Chart (Socket Head Cap Screws) as a free PDF — perfect for the shop wall or toolbox.
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