This page provides standard metric cap screw dimensions in accordance with ISO 4762. The tables include socket head cap screw sizes, thread pitch, head diameter, and hex socket dimensions for common metric sizes from M3 to M24.
A cap screw is a precision fastener with a cylindrical head and internal hex socket, commonly used in machinery and engineering assemblies. Socket head cap screws provide high strength and are typically manufactured to ISO 4762 standards.
Use the tables below to quickly find standard dimensions for socket head cap and countersunk socket screws including head size, thread pitch, and hex key size.
Notes:
All linear dimensions in milli metres
Dimensions generally to BS EN ISO 4762 BS 3643- 2 & BS 4168 (superceded)
Table shows: Thread pitch, hex socket size, head diameter, and socket depth for standard metric cap screws.
| Nominal | Thread. | Hex Socket Size | Body diameter and Head height | Head Dia | Soc. length | ||
| Size | Pitch | Max | Min | Max | Min | ||
| J | D /H | A | K | ||||
| M3 | 0.5 | 2.50 | 3.00 | 2.86 | 5.50 | 5.20 | 1.3 |
| M4 | 0.70 | 3.00 | 4.00 | 3.82 | 7.00 | 6.64 | 2.00 |
| M5 | 0.8 | 4.00 | 5.00 | 4.82 | 8.50 | 8.14 | 2.70 |
| M6 | 1.0 | 5.00 | 6.00 | 5.82 | 10.00 | 9.64 | 3.30 |
| M8 | 1.25 | 6.00 | 8.00 | 7.78 | 13.00 | 12.57 | 4.3 |
| M10 | 1.5 | 8.00 | 10.00 | 9.78 | 16.00 | 15.57 | 5.50 |
| M12 | 1.75 | 10.00 | 12.00 | 11.73 | 18.00 | 17.57 | 6.60 |
| M16 | 2.0 | 14.00 | 16.00 | 15.73 | 24.00 | 23.48 | 8.80 |
| M20 | 2.5 | 17.00 | 20.00 | 19.67 | 30.00 | 29.48 | 10.70 |
| M24 | 3.0 | 19.00 | 24.00 | 23.67 | 36.00 | 35.38 | 12.90 |
Table shows: Thread pitch, hex socket size, head diameter, and socket depth for standard metric countersunk socket screws.
The dimensions are generally in accordance with BS EN ISO 10642:1998. This supersedes BS 4168-8.
| Nominal size | Body Dia | Thread Pitch | Hex Socket Size | Max Cone Dia | Head Dia | Head Height | Soc. length | ||
| D(max) | D(min) | J | A1 | A_max | A_Min | H | K | ||
| M3 | 3.00 | 2.86 | 0.5 | 2,0 | 6,72 | 6,00 | 5,82 | 1,86 | 1,05 |
| M4 | 4.00 | 3.82 | 0.70 | 2,5 | 8,96 | 8,00 | 7,78 | 2,48 | 1,49 |
| M5 | 5.00 | 4.82 | 0.8 | 3,0 | 11,2 | 10,00 | 9,78 | 3,1 | 1,86 |
| M6 | 6.00 | 5.82 | 1.0 | 4,0 | 13,44 | 12,00 | 11,75 | 3,72 | 2,16 |
| M8 | 8.00 | 7.78 | 1.25 | 5,0 | 17,92 | 16,00 | 15,73 | 4,96 | 2,85 |
| M10 | 10.00 | 9.78 | 1.5 | 6,0 | 22,4 | 20,00 | 19,67 | 6,2 | 3,60 |
| M12 | 12.00 | 11.73 | 1.75 | 8,0 | 26,88 | 24,00 | 23,67 | 7,44 | 4,35 |
| M16 | 16.00 | 15.73 | 2.0 | 10,0 | 33,6 | 32,00 | 29,67 | 8,8 | 4,89 |
| M20 | 20.00 | 19.67 | 2.5 | 10,0 | 40,32 | 40,00 | 35,61 | 10,16 | 5,49 |