All charts / Hardware
Socket & Wrench Size Chart
SAE fractional sizes with the metric sizes used for the same fasteners.
| SAE | Metric |
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Standard: ASME B107 / ISO 272 · Data checked: 2026-10-14
Frequently asked questions
Why is my metric socket loose on an imperial bolt?
Because the sizes are close but not equal. A 13 mm socket is 0.512 in and a 1/2 in socket is 12.7 mm, a difference of 0.3 mm — enough to rock and to round the corners under load. Matching near-equivalents is fine for finger-tight work and destructive on a tight fastener.
What is the difference between 1/4, 3/8 and 1/2 inch drive?
The drive is the square that goes into the ratchet, and it is about how much torque the tool can take, not about the socket size. 1/4 in drive for small fasteners, 3/8 in for general work, 1/2 in and above for anything that needs real force. Using a small drive on a big fastener shears the square.
What is a deep socket for?
Reaching a nut that sits on a length of stud, or a fastener recessed behind something. A standard socket will bottom out on the stud before it reaches the nut. Deep sockets are also useful for spark plugs and for nuts where the thread protrudes.
Are impact and hand sockets the same?
No. Impact sockets are made from a softer, tougher steel and are meant for the hammering of an impact wrench; chrome hand sockets are harder and can shatter under impact. Never put a chrome socket on an impact driver — that is why impact sockets exist and why they are usually black.