Metric Socket Head Cap Screw Size Chart
Quick answer: the hex key is selected by the screw’s internal socket size, not by its thread diameter. For example, an ISO 4762 M6 socket head cap screw uses a 5 mm hex key; M8 uses 6 mm and M10 uses 8 mm.
ISO 4762 Socket Head Cap Screw Dimensions
This reference lists nominal dimensions for common metric socket head cap screws. The pitch column shows the coarse series only; fine-pitch screws may also be available. Standards, tolerances, and product variants can differ, so verify the fastener marking or manufacturer drawing when exact fit or strength matters.
| M1.6 | 1.5 | 3 | 1.6 | 0.35 |
|---|---|---|---|---|
| M2 | 1.5 | 4 | 2 | 0.40 |
| M2.5 | 2 | 4.5 | 2.5 | 0.45 |
| M3 | 2.5 | 5.5 | 3 | 0.50 |
| M4 | 3 | 7 | 4 | 0.70 |
| M5 | 4 | 8.5 | 5 | 0.80 |
| M6 | 5 | 10 | 6 | 1.00 |
| M8 | 6 | 13 | 8 | 1.25 |
| M10 | 8 | 16 | 10 | 1.50 |
| M12 | 10 | 18 | 12 | 1.75 |
| M14 | 12 | 21 | 14 | 2.00 |
| M16 | 14 | 24 | 16 | 2.00 |
| M18 | 14 | 27 | 18 | 2.50 |
| M20 | 17 | 30 | 20 | 2.50 |
| M22 | 17 | 33 | 22 | 2.50 |
| M24 | 19 | 36 | 24 | 3.00 |
| M27 | 19 | 40 | 27 | 3.00 |
| M30 | 22 | 45 | 30 | 3.50 |
| M33 | 24 | 50 | 33 | 3.50 |
| M36 | 27 | 54 | 36 | 4.00 |
| M42 | 32 | 63 | 42 | 4.50 |
| M48 | 36 | 72 | 48 | 5.00 |
22 rows
Scroll horizontally to view all columns.
How to Use the Chart
- Match the thread designation and standard before ordering.
- Use the listed hex key size for the internal socket; fully seat the key and avoid worn or undersized tools.
- Check pitch and length separately; diameter alone does not identify the complete fastener.
- For a replacement, match material, property class, coating, and application requirements as well as dimensions.
Related references: Allen wrench size chart, socket sizes in order, and bolt spanner size chart.
Manufacturer References
Wiha’s socket head cap screw key-size chart and Fastenal’s ISO 4762 datasheet provide additional dimensional details. Use the applicable standard and manufacturer documentation for controlled or safety-critical assemblies.
