Metric thread dimensions, head types and drive sizes.Fastener size guide
| Thread | Major Ø (mm) | Pitch (mm) | Across flats (mm) | Head height (mm) |
|---|---|---|---|---|
| M3 | 3.0 | 0.50 | 5.5 | 2.0 |
| M4 | 4.0 | 0.70 | 7.0 | 2.8 |
| M5 | 5.0 | 0.80 | 8.0 | 3.5 |
| M6 | 6.0 | 1.00 | 10.0 | 4.0 |
| M8 | 8.0 | 1.25 | 13.0 | 5.3 |
| M10 | 10.0 | 1.50 | 16.0 | 6.4 |
| M12 | 12.0 | 1.75 | 18.0 | 7.5 |
| M16 | 16.0 | 2.00 | 24.0 | 10.0 |
| M20 | 20.0 | 2.50 | 30.0 | 12.5 |
| M24 | 24.0 | 3.00 | 36.0 | 15.0 |
The first number is 1/100 of the nominal tensile strength in MPa (8 → 800 MPa). The second is the ratio of yield to tensile strength (0.8 → 80%).
Coarse pitch is the default for general engineering. Fine pitch resists vibration loosening and is used where thread engagement length is limited.