Inputs
Nominal size (M5 to M24) and nominal length l under the head.
Bolts · dimensions
ISO 4762 Socket Head Cap Screw Dimensions
ISO 4762 (DIN EN ISO 4762) standardizes socket head cap screws with a hexagon socket drive. The slim, small-diameter head suits counterbored holes and confined installations; head diameter, head height and the matching hexagon socket size are the dimensions that drive the joint design.
External-drive hex bolt alternative: ISO 4014 dimensions. Tightening torque: Tightening Torque.
ISO4762
02
Standard dimensions
Enter nominal size and length.
Inputs and method
Size a socket head cap screw to ISO 4762
Determine head and hexagon socket dimensions of a socket head cap screw from nominal size.
Calculation
A pure table lookup from Table 1 of the standard: head diameter, head height, hexagon socket size and minimum socket depth are fixed per nominal size, independent of length.
Example
M10x40: head diameter dk=16.0 mm, head height k=10.0 mm, hexagon socket s=8 mm, socket depth at least 5 mm.
Sources and limits: DIN EN ISO 4762:2004-06, Table 1.
Size a socket head cap screw to ISO 4762 in detail
Determine head and hexagon socket dimensions of a socket head cap screw from nominal size.
Why is a socket head cap screw's head smaller than a hex bolt's?
The hexagon socket drive transmits tightening torque through a tool surface inside the head's outline rather than across external flats. That lets the head diameter run markedly smaller than a hex bolt of the same nominal diameter -- for M10, about 16.0 mm versus an 18.9 mm width across corners. This allows more compact counterbores and use in confined spaces, but requires sufficient tool engagement depth to transmit the higher tightening torque without cam-out.
Formula and variables
A pure table lookup from Table 1 of the standard: head diameter, head height, hexagon socket size and minimum socket depth are fixed per nominal size, independent of length.
Choose the inputs correctly
Nominal size (M5 to M24) and nominal length l under the head.
How to use the calculator
Enter nominal size and nominal length. The calculator returns head diameter and height for counterbore design plus the matching hexagon socket size and minimum socket depth for tool selection.
Worked example
M10x40: head diameter dk=16.0 mm, head height k=10.0 mm, hexagon socket s=8 mm, socket depth at least 5 mm.
What does the socket depth t refer to?
The minimum socket depth t is how deep a correctly sized hexagon key must seat in the head to transmit the standard's tightening torque without rounding the socket flanks. With a worn or undersized tool, shallower engagement often isn't enough -- the result is a slipping key and a damaged screw, not a failure of the screw itself.
All dimensions in millimetres.
Typical applications
Sizing counterbores in housing parts, selecting the correct hexagon socket size for a torque wrench, comparing against hex bolts under space constraints.
Assumptions, limits and common mistakes
DIN EN ISO 4762:2004-06, Table 1.
Common mistake: Don't use the head diameter dk directly as the counterbore dimension -- dk is a maximum, and the bore additionally needs clearance or a relief that this calculation does not include.
Frequently asked questions
What tool size do I need for an M10 socket head cap screw?
A hexagon key of size 8 mm (s = 8 mm) to ISO 23429, with a minimum socket depth of 5 mm for full tool engagement.
Must the head diameter dk always be met exactly?
dk is a standard maximum. The actual counterbore design needs additional clearance for manufacturing tolerances; this calculation gives only the screw's standard dimension, not the bore design.