Wire diameter is a premier factor in determining the wire mesh specification. There are normally fours ways to identify the wire diameters: BWG, SWG or by mm or by inch. 

Gauge is a measurement of wire thickness. There are some different national systems of gauge sizes, French, British, US, Berminham, etc. As the same gauge number in different countries refers to different wire diameters, this has become a great cause of confusion. So nowadays, we usually use wire diameter in mm or in inch instead of gauge number to specify our products.

How Wire Gauge Gets it Name: The wire gage system used by practically all the steel producers in the United States is known by the name Steel Wire Gage or to distinguish if from the Standard Wire Gage (S.W.G.) used in Great Britain it is called he United States Steel Wire Gage.

In Great Britain one wire gage has been legalized. This is called the Standard Wire Gage (S.W.G.), formerly called Imperial Wire Gage.

S.W.G., B.W.G., MM, INCH. Comparisons Table: