Standard wire gauge

A standard wire gauge.

British Standard Wire Gauge is a set of wire sizes given by BS 3737:1964 (now withdrawn), and is generally abbreviated to SWG.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

SWG was fixed by Order of Council August 23, 1883. It was constructed by improving the Birmingham Wire Gauge. It was made legal standard March 1, 1884 by the British Board of Trade. SWG is not to be confused with American Wire Gauge which has a similar but not quite interchangeable numbering scheme.

The basis of the system is the thou, (or mil in US English) or 0.001 in. No. 7/0, the largest size, is 0.50 in. (500 thou or 12.7 mm) in diameter, and the smallest, No. 50, is 0.001 in. (1 thou or about 25 µm) in diameter. The wire diameter diminishes with increasing gauge size. Between each gauge, the weight diminishes by approximately 20%. Because the weight per unit length is related to the area, and therefore the square of the diameter, the diameter diminishes by approximately 10.6%:

A table of wire gauges and diameters is shown below.^[1][2] The relationship of diameter to gauge is piecewise linear, only approximating a (constant-ratio) exponential curve.

See also

• Wire gauge comparison chart
• IEC 60228, the metric wire-size standard used in most parts of the world.
• Circular mil, Electrical industry standard for wires larger than 4/0.
• American Wire Gauge (AWG), used primarily in the US and Canada
• Stubs Iron Wire Gauge
• Jewelry wire gauge
• Body jewelry sizes
• Electrical wiring
• Number 8 wire, a term used in the New Zealand vernacular

References