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General Data > Wire Gauges

Wires purchased through lab suppliers, whether they are copper, nickel-chromium or steel are usually advertised by their SWG value, that is the thickness of the wire. SWG stands for Standard Wire Gauge and is the British legal standard. The higher the SWG number, the thinner the wire.

Below is a conversion chart showing the SWG value against the diameter if the wire in millimetres:

S.W.G. Diameter (mm)
16
1.626
18
1.219
20
0.914
22
0.711
24
0.559
26
0.457
28
0.376
30
0.315
32
0.274
34
0.234
36
0.193
38
0.152
40
0.122
42
0.102

When issuing wires for practicals such as electrical resistance investigations, ensure wire looms are clearly marked with the SWG and perhaps the diameter in millimetres. The diameter and therefore the SWG of an unmarked wire can be calculated using a micrometer.