Standard ChartsMetric Charts

Welcome to Socket Size where we strive to help you get the most utility from your sockets and wrenches. Do you find converting sockets between metric and standard measurement sizes confusing? We can help!

Socket conversions between metric and standard can be confusing if you are familiar with one measurement system but not the other. can help with that, and many other fastener, socket and wrench related challenges. Thanks for visiting.

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Standard Socket Sizes

Standard Socket Size Chart

See the standard socket sizes, sorted from smallest to largest, for each standard socket set and drive size.

Frequently asked questions

These are some of the more commonly asked questions about standard vs metric socket use.

Is SAE Standard or Metric?

SAE stands for "Society of Automotive Engineers". The society of automotive engineers standardized the use of"hes and fractions of"hes when measuring nuts and bolts on vehicles built"America circa 1970. SAE is standard and measured"inches.

What is the difference between standard and metric sockets?

The difference between standard and metric sockets is the measurement system they use and, correspondingly, the sizes they are. A standard socket is measured and sized"inches whereas a metric socket is measured and sized"millimeters(mm).

How do I know what size socket I have?

Socket size is marked on the side of each socket. On metric sockets it will be marked"millimeters, example: 10mm. On standard sockets it will be marked"inches and fractions of"hes. Example: 1 1/4in.

Sockets that don't have a size marked on the side can be measured by seeing how wide the space is"ide the socket, or by finding a bolt or nut with a known size that the socket fits over snugly.

How do I know what size ratchet I need?

The size of ratchet needed for any particular socket is determined by the size of the square connecting end of the socket. Smaller sockets will have a square opening as small as 1/4"h while larger sockets have a square opening of up to 1"h. The ratchet drive must be of the same size as the square end of the socket or it will not fit.

Note: A socket adapter can be used to allow a ratchet drive to work on a socket designed for a different ratchet size. Also, only the square end of a socket should connect to a ratchet. The 6 and 12 point end of the socket is for grasping fasteners like nuts and bolts.

What is the most common ratchet size?

The most common ratchet size for home use is the 3/8"h drive ratchet followed closely by the 1/4"h drive and 1/2"h drive ratchets. It should be noted that different tasks will require different socket sizes based on the fastener size of the object being worked on. Small engines, for example, use smaller bolts than larger vehicle engines.

Warning: Using a socket of the wrong measurement type on a fastener can damage the fastener, especially if the fastener is already worn, rusted or stuck.

Using standard sockets on metric bolts, and vice versa, can work but there is an increased risk of rounding, stripping or breaking the fasterner. Always use caution, even with the right tools.

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