Metric Socket Head Cap Screw Size Chart
Quick answer: metric socket head cap screws use an internal hex key that is smaller than the screw thread diameter. Common examples include M6 with a 5 mm hex key, M8 with a 6 mm hex key, M10 with an 8 mm hex key, and M12 with a 10 mm hex key.
Metric Socket Head Cap Screw Dimensions
| Screw size | Hex key size | Head diameter approx. | Head height approx. | Coarse pitch |
|---|---|---|---|---|
| M3 | 2.5 mm | 5.5 mm | 3 mm | 0.5 mm |
| M4 | 3 mm | 7 mm | 4 mm | 0.7 mm |
| M5 | 4 mm | 8.5 mm | 5 mm | 0.8 mm |
| M6 | 5 mm | 10 mm | 6 mm | 1.0 mm |
| M8 | 6 mm | 13 mm | 8 mm | 1.25 mm |
| M10 | 8 mm | 16 mm | 10 mm | 1.5 mm |
| M12 | 10 mm | 18 mm | 12 mm | 1.75 mm |
| M14 | 12 mm | 21 mm | 14 mm | 2.0 mm |
| M16 | 14 mm | 24 mm | 16 mm | 2.0 mm |
| M20 | 17 mm | 30 mm | 20 mm | 2.5 mm |
| M24 | 19 mm | 36 mm | 24 mm | 3.0 mm |
| M30 | 22 mm | 45 mm | 30 mm | 3.5 mm |
| M36 | 27 mm | 54 mm | 36 mm | 4.0 mm |
How To Use The Chart
- Use the thread size to identify the screw, then choose the matching hex key.
- Confirm whether the screw follows ISO 4762, DIN 912, or another standard.
- For tight screws, use a full-depth hex key or bit socket instead of a worn ball-end key.
- Check strength class, thread pitch, and length before ordering replacements.
Related references: Allen wrench size chart, socket sizes in order, and bolt spanner size chart.
Source Notes
Dimensions were checked against ISO 4762/DIN 912 socket head cap screw references including Wiha’s socket head cap screw key size chart, RoyMech metric cap screw tables, and metric fastener datasheets. Confirm the specific standard for critical hardware.
