American wire gauge

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American wire gauge (AWG), also known as the "Brown and Sharpe" wire gauge, is used in the United States and other countries as a standard method of denoting wire diameter, especially for nonferrous, electrically conducting wire. The steel industry uses a different numbering system for their wire thickness gages (e.g. W&M Wire Gage or US Steel Wire Gage or the different Music Wire Gage) so data below does not apply to steel wire.

Increasing gauge numbers give decreasing wire diameters, which is similar to many other non-metric gauging systems. This seemingly-counterintuitive numbering is derived from the fact that the gauge number is related to the number of drawing operations that must be used to produce a given gauge of wire; very fine wire (for example, 30 gauge) requires far more passes through the drawing dies than does 0 gauge wire.

Note that for gauges 5 through about 14, the wire gauge is effectively the number of bare solid wires that, when placed side by side, span 1 inch. That is, 8 gauge is about 1/8" in diameter.

In the same fashion, AWG is also commonly used to specify body piercing jewelry sizes, especially smaller sizes.[1]

1 Formulae
2 Table of AWGs and approximate corresponding sizes
3 Reference
4 See also
5 External links

[edit] Formulae

By definition, No. 36 AWG is 0.005 inches diameter, and No. 0000 is 0.46 inches diameter. The ratio of these sizes is 92, and between them are 38 sizes, with equal ratios between each adjacent pair of sizes. (The 40 different sizes result in 39 size changes.) (Sizes with multiple zeros are sucessively larger than No. 0 and can be denoted using "number of zeros/0", e.g. 5/0 for 00000.) Therefore, the diameter of a No. n AWG wire is

$d_n = 0.005~\mathrm{in} \times 92 ^ \frac{36-n}{39}$

and its cross-section area is

$A_n = \frac{\pi}{4} d_n^2 = 0.000019635~\mathrm{in}^2 \times 92 ^ \frac{36-n}{19.5}$ .

For an m/0 AWG wire, use n = −(m−1) in the above formulas. For instance for No. 0000 or 4/0, use n = -3.

The ratio between successive sizes is the 39th root of 92, or approximately 1.1229322. [2]

The sixth power of this ratio is very close to 2, which means for an increase in 6 gauge numbers, the wire diameter is changed by a ratio of two (No. 10 is about one-half the diameter of No. 4 AWG). A decrease of three gauge numbers doubles the area of a wire. A decrease of 10 gauge numbers, for example from No. 10 to 1/0, multiplies the area and weight by approximately 10 and reduces the resistance by approximately 10.

[edit] Table of AWGs and approximate corresponding sizes

The table below shows various data including both the resistance of the various wire gauges and the allowable current (ampacity) based on plastic insulation. The diameter information in the table applies to solid wires. Stranded wires are calculated by calculating the equivalent cross sectional copper area. The table below assumes DC or frequencies equal to or less than 60 Hz, and does not take skin effect into account.

AWG	Diameter		Area		Copper resistance	Copper resistance^[3]	Copper wire current rating with 60 °C insulation	Approximate stranded metric equivalents
	(in)	(mm)	(kcmil)	(mm²)	(Ω/1 km)	(Ω/1000 ft)	(A)
000000(6/0)	0.5800	14.73	336.5	170
00000(5/0)	0.5165	13.12	266.8	135
0000(4/0)	0.4600	11.68	211.6	107
000(3/0)	0.4096	10.40	167.8	85
00(2/0)	0.3648	9.266	133.1	67.4
0(1/0)	0.3249	8.251	105.5	53.5	~0.3281	~0.1
1	0.2893	7.348	83.69	42.4			110
2	0.2576	6.544	66.37	33.6			95
3	0.2294	5.827	52.63	26.7			85	196/0.4
4	0.2043	5.189	41.74	21.2			70
5	0.1819	4.621	33.10	16.8				126/0.4
6	0.1620	4.115	26.25	13.3			55
7	0.1443	3.665		10.5				80/0.4
8	0.1285	3.264		8.37			40
9	0.1144	2.906		6.63				>84/0.3
10	0.1019	2.588		5.26	3.2772	0.9989	30	<84/0.3
11	0.0907	2.305		4.17	4.1339	1.260		56/0.3
12	0.0808	2.053		3.31	5.210	1.588	20
13	0.0720	1.828		2.62	6.572	2.003		50/0.25
14	0.0641	1.628		2.08	8.284	2.525	15
15	0.0571	1.450		1.65	10.45	3.184		>30/0.25
16	0.0508	1.291		1.31	13.18	4.016	10	<30/0.25
17	0.0453	1.150		1.04	16.614	5.064		32/0.2
18	0.0403	1.02362		0.823	20.948	6.385		>24/0.2
19	0.0359	0.9116		0.653	26.414	8.051		<24/0.2
20	0.0320	0.8128		0.518	33.301	10.15		16/0.2
21	0.0285	0.7229		0.410	41.995	12.80
22	0.0253	0.6438		0.326	52.953	16.14		7/0.25
23	0.0226	0.5733		0.258	66.798	20.36
24	0.0201	0.5106		0.205	84.219	25.67		1/0.5, 7/0.2, 30/0.1
25	0.0179	0.4547		0.162	106.201	32.37
26	0.0159	0.4049		0.129	133.891	40.81		7/0.15
27	0.0142	0.3606		0.102	168.865	51.47
28	0.0126	0.3211		0.081	212.927	64.90
29	0.0113	0.2859		0.0642	268.471	81.83
30	0.0100	0.2546		0.0509	338.583	103.2		1/0.25, 7/0.1
31	0.0089	0.2268		0.0404	426.837	130.1
32	0.0080	0.2019		0.0320	538.386	164.1		1/0.2, 7/0.08
33	0.0071	0.1798		0.0254	678.806	206.9
34	0.0063	0.1601		0.0201	833	260.9
35	0.0056	0.1426		0.0160	1085.958	331.0
36	0.0050	0.1270		0.0127	1360.892	414.8
37	0.0045	0.1131		0.0100	1680.118	512.1
38	0.0040	0.1007		0.00797	2127.953	648.6
39	0.0035	0.08969		0.00632	2781.496	847.8
40	0.0031	0.07987		0.00501	3543.307	1080.0

The "Approximate stranded metric equivalents" column lists commonly available cables in the format "number of strands / diameter of individual strand (mm)" which is the common nomenclature describing cable construction within an overall cross-sectional area. Where a common cable is midway between two AWG sizes, it is listed and being > one AWG and < another AWG. Cables sold in Europe are normally labeled according to the combined cross section of all strands in mm², which can be compared directly with the Area column.

In the North American electrical industry, conductors larger than 4/0 AWG are generally identified by the area in thousands of circular mils (kcmil), where 1 kcmil = 0.5067 mm². A circular mil is the area of a wire one mil in diameter. One million circular mils is the area of a rod with 1000 mil = 1 in diameter. An older abbreviation for one thousand circular mils is mcm. The term 'mil' is capable of being misinterpreted because the term 'mil' is used sometimes as a colloquial term for millimetre, millilitre etc.

Outside North America, wire sizes for electrical purposes are usually given as the cross sectional area in square millimetres. International standard manufacturing sizes for conductors in electrical cables are defined in IEC 60228.

Ref 3: ↑ Bare, solid copper wire at 68 °F — Resistance data is from Belden Master Catalog, 1995.

[edit] Reference

Donald G. Fink and H. Wayne Beaty, Standard Handbook for Electrical Engineers, Eleventh Edition,McGraw-Hill, New York, 1978, ISBN 0-07-020974-X, page 4-18 and table 4-11.