SWG to mm free online calculator

Standard wire gauge (SWG) to mm and mm2 converison calculator, chart and how to convert.

mm
in
mm2

Wire cross sectional area calculation

The n gauge wire's cross sercional area An in square millimeters (mm2) is equal to pi divided by 4 times the square wire diameter d in millimeters (mm):

An (mm2) = (π/4)×dn2

SWG to mm conversion chart

SWG # Diameter
(mm)
Area
(mm2)
7/0 12.700 126.6769
6/0 11.786 109.0921
5/0 10.973 94.5638
4/0 10.160 81.0732
3/0 9.449 70.1202
2/0 8.839 61.3643
0 8.230 53.1921
1 7.620 45.6037
2 7.010 38.5989
3 6.401 32.1780
4 5.893 27.2730
5 5.385 22.7735
6 4.877 18.6793
7 4.470 15.6958
8 4.064 12.9717
9 3.658 10.5071
10 3.251 8.3019
11 2.946 6.8183
12 2.642 5.4805
13 2.337 4.2888
14 2.032 3.2429
15 1.829 2.6268
16 1.626 2.0755
17 1.422 1.5890
18 1.219 1.1675
19 1.016 0.8107
20 0.914 0.6567
21 0.813 0.5189
22 0.711 0.3973
23 0.610 0.2919
24 0.559 0.2452
25 0.5080 0.2027
26 0.4572 0.1642
27 0.4166 0.1363
28 0.3759 0.1110
29 0.3454 0.0937
30 0.3150 0.0779
31 0.2946 0.0682
32 0.2743 0.0591
33 0.2540 0.0507
34 0.2337 0.0429
35 0.2134 0.0358
36 0.1930 0.0293
37 0.1727 0.0234
38 0.1524 0.0182
39 0.1321 0.0137
40 0.1219 0.0117
41 0.1118 0.0098
42 0.1016 0.0081
43 0.0914 0.0066
44 0.0813 0.0052
45 0.0711 0.0040
46 0.0610 0.0029
47 0.0508 0.0020
48 0.0406 0.0013
49 0.0305 0.0007
50 0.0254 0.0005

SWG definition

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Gauge (often abbreviated to Standard Wire Gauge or SWG) is a unit for denoting wire size given by BS 3737:1964 (now withdrawn).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 is 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.

SWG was fixed by Order of Council August 23, 1883. It was constructed by improving the Birmingham Wire Gauge. It was made a legal standard on 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 interchangeable numbering scheme.

A table of the gauge numbers and wire diameters is shown below. The basis of the system is the thou (or mil in US English), or 0.001 in. Sizes are specified as wire diameters, stated in thou and tenths of a thou (mils and tenths). The wire diameter diminishes with increasing size number. No. 7/0, the largest size, is 0.50 in. (500 thou or 12.7 mm) dia., No. 1 is 0.30 in. (300 thou), and the smallest, No. 50, is 0.001 in. (1 thou or about 25 µm).

The system as a whole approximates a (constant-ratio) exponential curve. The weight per unit length diminishes by an average of approximately 20% at each step. Because the weight per unit length is related to the cross sectional area, and therefore to the square of the diameter, the diameter diminishes by approximately 10.6%:

But the system is piecewise linear, only approximating the exponential curve loosely. Thus it runs in constant steps of 0.4 thou (0.4 mil) through the range No. 49 - No. 39 and 0.8 thou (0.8 mil) through No. 39 - No. 30.

source: Wikipedia

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