AWG Wire Gauge Standard Vs. SWG Wire Gauge Standard

American Wire Gauge or AWG is the standard way of measuring wire gauges in the United States. However, in other countries, they use a different standard of measuring, SWG or British Imperial Standard Wire Gauge, for example. The availability of two different standards has led to a difference in how wire gauges are measured and what standard sizes of wire are used.

AWG

AWG is the standard for measuring wire in the United States. This standard is defined by the diameter of the electrical wire that is being measured. Therefore, it is the physical size is what matters most. Also, the larger the physical size of the wire the smaller the wire gauge according to the AWG measurements.

SWG

SWG was the legal standard for measuring wire in the United Kingdom as of 1884. All of the SWG measurements are in metric sizes. In most cases of use of the SWG measuring standard the sizes will be rounded up which does affect the accuracy.

Similarities

In a lot of ways, AWG and SWG standards are similar. Most noteworthy, both standards are based on the physical size of the wire being measured. Also, both share common wire numbers that express those physical sizes. Finally, metal measuring plates are used to determine the size of the wire.

Differences

The most obvious difference is the standard of measurements. AWG is recorded in what is referred to as the imperial system of measurement. This system of measurements is in inches. Therefore, the American standard is different from the SWG system which uses the metric system of measuring. When looking at the charts below there are slight differences in the calculations between the two systems. Especially relevant is the difference that can be seen between the 12 and 24 gauges. These are very common sizes of wire and the chart shows a very drastic difference amongst the size measurements.

Reference charts:

Wire Number	Imperial Standard Wire Gauge	American Wire Gauge
gauge	ins. dia.	ins. dia.
0000000 (7/0)	0.5000	–
000000 (6/0)	0.4640	0.580000
00000 (5/0)	0.4320	0.516500
0000 (4/0)	0.4000	0.460000
000 (3/0)	0.3720	0.409642
00 (2/0)	0.3480	0.364796
0 (1/0)	0.3240	0.324861
1	0.3000	0.289297
2	0.2760	0.257627
3	0.2520	0.229423
4	0.2320	0.2043
5	0.2120	0.1819
6	0.1920	0.1620
7	0.1760	0.1443
8	0.1600	0.1285
9	0.1440	0.1144
10	0.1280	0.1019
11	0.1160	0.0907
12	0.1040	0.0808
13	0.0920	0.0720
14	0.0800	0.0641
15	0.0720	0.0571
16	0.0640	0.0508
17	0.0560	0.0453
18	0.0480	0.0403
19	0.0400	0.0359
20	0.0360	0.0320
21	0.0320	0.0285
22	0.0280	0.0253
23	0.0240	0.0226
24	0.0220	0.0201
25	0.0200	0.0179
26	0.0180	0.0159
27	0.0164	0.0142
28	0.0148	0.0126
29	0.0136	0.0113
30	0.0124	0.0100
31	0.0116	0.0089
32	0.0108	0.0080
33	0.0100	0.0071
34	0.0092	0.0063
35	0.0084	0.0056
36	0.0076	0.0050
37	0.0068	0.0045
38	0.0060	0.0040
39	0.0052	0.0035
40	0.0048	0.0031
41	0.0044	0.0028
42	0.0040	0.0025
43	0.0036	0.0022
44	0.0032	0.0020
45	0.0028	0.0018
46	0.0024	0.0016
47	0.0020	0.0014
48	0.0016	0.0012
49	0.0012	0.0011
50	0.0010	0.0010
51	–	0.00088
52	–	0.00078
53	–	0.00070
54	–	0.00062
55	–	0.00055
56	–	0.00049