British Standard Wire Gauge (often abbreviated to Standard Wire Gauge or SWG) is a unit for denoting wire size given by BS 3737:1964 (now withdrawn). It is also known as the Imperial Wire Gauge or British Standard Gauge. Use of SWG sizes has fallen greatly in popularity, but they are still used as a measure of thickness in guitar strings and some electrical wire. Cross sectional area in square millimetres is now the more usual size measurement for wires used in electrical installation cables. The current British Standard for metallic materials such as wire and sheet is BS 6722:1986, which is a solely metric standard.
