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.