SAE or Standard: A standard or SAE (Society of Automotive Engineers) wrench is measured in fractions of inches. Small wrenches will be around 1/4 inches, while large wrenches will be 1 inch or larger. A small metric wrench would measure about 8 mm, while a large one would be about 20 mm.

Most common are the 1/4-inch, 3/8-inch and ½-inch ratchet drivers, but ¾-inch and 1-inch sets are available for heavy-duty work.

Metric and SAE wrenches have different systems of measurement. Metric sockets and wrenches use the metric measurement system. SAE wrenches use the imperial measurement system, mostly used in the United States, where it’s described using inches, or fractions of an inch.

Metric is the preferred fastener measurement throughout the world. More exact than fractions of an inch, metric measurements–based on millimeters–are a precise representation of the diameter of the head of the fastener.

The following are five types of wrenches that will be handy to have in your toolbox:

• Open-end wrench. This one-piece wrench is made double-ended with differing size openings for opposite faces of bolts or nuts.
• Combination wrench.
• Allen wrench.
• Socket wrench.
• Adjustable wrench.

Metric and SAE fasteners are measured differently and with different vocabulary. SAE nuts, bolts and screws are measured by their thread count, or TPI (threads per inch) and their length. Metric fasteners are measured by length and pitch, or the distance between threads.

While there is no precise correlation between SAE fractional and metric measurements, there are many sockets that are close enough in size to be used interchangeably, in some circumstances. For example, 5/16 and 8 mm, 7/16 and 11 mm, 5/8 and 16 mm, 3/4 and 19 mm, 7/8 and 22 mm, and 15/16 and 24 mm.

Should I buy metric or SAE wrenches?

The standard wrench is made more specifically for use in North America as the measurement is in the American system. The inches and feet calculation is the American system. Whereas, the metric wrenches can be used with nuts and bolts that have been made according to the metric measurements.

Standard Combination Wrenches (1/4,5/16,11/32,3/8,7/16,1/2,9/16,5/8,11/16,3/4,13/16,7/8,15/16,1)

SAE stands for the Society of Automotive Engineers and refers in this case to tools whose size is marked and aligned with fractions of an inch, eg.

These wrenches can deliver 200-400 ft/lbs. of torque. Metric bolt sizes range from 10 mm to 24 mm. Odd diameters such as 19 mm and 21 mm become common in this range. Standard bolt sizes range from 5/16-inches to 1 inch, again increasing in increments of 1/16-inch.

“SAE” is a shorthand for a set of standard size parts and tools in USCS (e.g. 1/2″ bolt head and 1/2″ wrench). What is now SAE International started in the US, in 1905, as the Society of Automobile Engineers, to interchange solutions to common problems in automobiles,…