Socket Size Chart — Metric to Imperial Quick Reference
| Metric (mm) | Imperial (SAE) approx. |
|---|---|
| 8mm | 5/16" |
| 10mm | 3/8" |
| 11mm | 7/16" |
| 13mm | 1/2" |
| 14mm | 9/16" |
| 15mm | 9/16" |
| 17mm | 11/16" |
| 19mm | 3/4" |
| 22mm | 7/8" |
| 24mm | 15/16" |
| 27mm | 1-1/16" |
| 30mm | 1-3/16" |
| 32mm | 1-1/4" |
Metric and imperial socket sizes are NOT interchangeable — close sizes will round fastener heads. Always match socket to fastener system. Drive size (1/4", 3/8", 1/2") is the ratchet connection — separate from the socket's fastener size. Shallow sockets for standard bolt heads; deep sockets for spark plugs, long studs, or recessed fasteners.
People Also Ask — Socket Size Chart: Metric, Imperial & Drive Sizes
Q: What is the difference between 3/8" and 1/2" drive sockets?
Drive size refers to the square drive that connects the socket to the ratchet — 3/8" is the most versatile for general trade work, while 1/2" drive handles higher torque applications like wheel nuts and structural bolts. 1/4" drive suits tight spaces and small fasteners; 3/4" and 1" drive are for heavy industrial work.
Q: Can I use a metric socket on an imperial bolt?
In a pinch, a close-fitting metric socket can work on an imperial fastener — for example, a 15 mm socket is nearly identical to 19/32". However, using a slightly oversized socket risks rounding off the fastener corners. Always use the correct size where possible; keep a mixed metric/imperial set for older equipment.
Q: What does 6-point vs 12-point socket mean?
A 6-point socket has six contact surfaces and grips flat-to-flat on the hex, reducing the risk of rounding fasteners. A 12-point socket engages on corners, making it easier to position in tight spaces but more likely to slip under high torque. Use 6-point sockets for stuck or high-torque fasteners; 12-point for easy access work.
Q: Are impact sockets different from standard sockets?
Yes — impact sockets are made from thicker, softer chrome-molybdenum steel that absorbs the hammering action of an impact wrench without shattering. Standard chrome-vanadium hand sockets can crack under impact loads. Impact sockets are typically black (not chrome-plated) for easy identification. Never use hand sockets with impact guns.
