SHOP REFERENCE / SAE SOCKETS
SAE Socket Size Chart
Choose a socket by the width across the flat sides of the nut or bolt head. The chart lists common inch openings from smallest to largest; check the size stamped on your socket and test the fit on the actual fastener.
Open the Socket Finder toolA standard 3/8 in. US hex bolt typically takes a 9/16 in. socket: bolt thread diameter and hex head width are different measurements.
Common SAE socket sizes
Examples apply to standard external hex heads only; a different fastener style or standard may use a different head size.
| Socket opening | Example or fitting note |
|---|---|
| 5/32 in. | Small hex fasteners |
| 3/16 in. | Small hex fasteners |
| 7/32 in. | Small hex fasteners |
| 1/4 in. | Small hex fasteners |
| 9/32 in. | Small hex fasteners |
| 5/16 in. | Small hex fasteners |
| 11/32 in. | Small hex fasteners |
| 3/8 in. | Hex heads measuring 3/8 in. across flats |
| 7/16 in. | Standard 1/4 in. hex bolt head |
| 1/2 in. | Standard 5/16 in. hex bolt head |
| 9/16 in. | Standard 3/8 in. hex bolt head |
| 5/8 in. | Standard 7/16 in. hex bolt head |
| 11/16 in. | Hex heads measuring 11/16 in. across flats |
| 3/4 in. | Standard 1/2 in. hex bolt head |
| 13/16 in. | Standard 9/16 in. hex bolt head |
| 7/8 in. | Hex heads measuring 7/8 in. across flats |
| 15/16 in. | Standard 5/8 in. hex bolt head |
| 1 in. | Hex heads measuring 1 in. across flats |
| 1-1/16 in. | Hex heads measuring 1-1/16 in. across flats |
| 1-1/8 in. | Standard 3/4 in. hex bolt head |
| 1-3/16 in. | Hex heads measuring 1-3/16 in. across flats |
| 1-1/4 in. | Hex heads measuring 1-1/4 in. across flats |
| 1-5/16 in. | Standard 7/8 in. hex bolt head |
| 1-3/8 in. | Hex heads measuring 1-3/8 in. across flats |
| 1-7/16 in. | Hex heads measuring 1-7/16 in. across flats |
| 1-1/2 in. | Standard 1 in. hex bolt head |
This chart shows a practical range, not the contents of any one kit. Some sets omit intermediate sizes or include larger ones. An example bolt head size is a nominal reference for a standard US hex bolt, not a substitute for measuring your fastener. Some 1/4 in. bolts have a 3/8 in. head instead of 7/16 in.; heavy hex and flange styles can differ.
CHOOSE THE SOCKET
6-point vs 12-point
Fits external hex heads at six positions. A snug 6-point socket is a useful first choice for high torque or a worn hex head because it has a broader fit against the hex flats.
Fits an external hex head in more starting positions and also fits a matching 12-point fastener. It can be convenient where ratchet movement is limited. Use the exact opening size and a snug fit.
Neither point count changes the opening size: a 9/16 in. socket is marked 9/16 in. in either style. The 1/4, 3/8, or 1/2 in. drive size is the square opening for the ratchet, not the size that fits over the fastener. Use an impact-rated socket with an impact wrench.
Match a bolt thread size to its hex head → See metric socket sizes → See metric and SAE sizes in order →Sources and scope
TEKTON’s 5/32–9/16 in. set, 1/4–1 in. set, and 3/8–1-1/2 in. set document the listed socket sizes. Bolt Depot’s US hex bolt head chart supports the selected standard hex head examples and the 1/4 in. bolt exception. GEARWRENCH’s 12-point socket details describe external hex and 12-point fit. Head style and manufacturing standards matter; measure across flats and confirm the fit.