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 gauges (for example, W&M Wire Gauge or US Steel Wire Gauge or the different Music Wire Gauge) 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 inches 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 References
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 successively larger than No. 0 and can be denoted using "number of zeros/0", for example 5/0 for 00000.) Therefore, the diameter of a No. n AWG wire is

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

and its cross-section area is

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

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 six gauge numbers, the wire diameter is changed by a ratio of 2 (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 ten 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 AC frequencies equal to or less than 60 Hz, and does not take skin effect into account. Turns of wire is on a best-case scenario when winding tightly packed coils.

AWG	Diameter		Turns of wire		Area		Copper resistance	Copper resistance^[3]	Copper wire current rating with 60 °C insulation	Approximate stranded metric equivalents
	(inch)	(mm)	(per inch)	(per cm)	(kcmil)	(mm²)	(Ω/1 km)	(Ω/1000 ft)	(A)
000000(6/0)	0.58	14.73	1.72	0.68	336.5	170
00000(5/0)	0.5165	13.12	1.94	0.76	266.8	135
0000(4/0)	0.46	11.68	2.17	0.85	211.6	107	0.16*	0.049*	250
000(3/0)	0.4096	10.4	2.44	0.96	167.8	85	0.2*	0.062*	???
00(2/0)	0.3648	9.266	2.74	1.08	133.1	67.4	0.25*	0.077*
0(1/0)	0.3249	8.251	3.08	1.21	105.5	53.5	~0.3281	~0.1
1	0.2893	7.348	3.46	1.36	83.69	42.4	0.4*	0.12*	110
2	0.2576	6.544	3.88	1.53	66.37	33.6	0.5*	0.15*	95
3	0.2294	5.827	4.36	1.72	52.63	26.7			85	196/0.4
4	0.2043	5.189	4.89	1.93	41.74	21.2	0.8*	0.24*	70
5	0.1819	4.621	5.5	2.17	33.1	16.8				126/0.4
6	0.162	4.115	6.17	2.43	26.25	13.3	1.5*	0.47*	55
7	0.1443	3.665	6.93	2.73		10.5				80/0.4
8	0.1285	3.264	7.78	3.06		8.37	2.2*	0.67*	40
9	0.1144	2.906	8.74	3.44		6.63				>84/0.3
10	0.1019	2.588	9.81	3.86		5.26	3.2772	0.9989	30	<84/0.3
11	0.0907	2.305	11.03	4.34		4.17	4.1339	1.26		56/0.3
12	0.0808	2.053	12.38	4.87		3.31	5.21	1.588	20
13	0.072	1.828	13.89	5.47		2.62	6.572	2.003		50/0.25
14	0.0641	1.628	15.6	6.14		2.08	8.284	2.525	15
15	0.0571	1.45	17.51	6.89		1.65	10.45	3.184		>30/0.25
16	0.0508	1.291	19.69	7.75		1.31	13.18	4.016	10	<30/0.25
17	0.0453	1.15	22.08	8.69		1.04	16.614	5.064		32/0.2
18	0.0403	1.02362	24.81	9.77		0.823	20.948	6.385		>24/0.2
19	0.0359	0.9116	27.86	10.97		0.653	26.414	8.051		<24/0.2
20	0.032	0.8128	31.25	12.30		0.518	33.301	10.15		16/0.2
21	0.0285	0.7229	35.09	13.81		0.41	41.995	12.8
22	0.0253	0.6438	39.53	15.56		0.326	52.953	16.14		7/0.25
23	0.0226	0.5733	44.25	17.42		0.258	66.798	20.36
24	0.0201	0.5106	49.75	19.59		0.205	84.219	25.67		1/0.5, 7/0.2, 30/0.1
25	0.0179	0.4547	55.87	22.00		0.162	106.201	32.37
26	0.0159	0.4049	62.89	24.76		0.129	133.891	40.81		7/0.15
27	0.0142	0.3606	70.42	27.72		0.102	168.865	51.47
28	0.0126	0.3211	79.37	31.25		0.081	212.927	64.9
29	0.0113	0.2859	88.5	34.84		0.0642	268.471	81.83
30	0.01	0.2546	100	39.37		0.0509	338.583	103.2		1/0.25, 7/0.1
31	0.0089	0.2268	112.36	44.24		0.0404	426.837	130.1
32	0.008	0.2019	125	49.21		0.032	538.386	164.1		1/0.2, 7/0.08
33	0.0071	0.1798	140.85	55.45		0.0254	678.806	206.9
34	0.0063	0.1601	158.73	62.49		0.0201	833	260.9
35	0.0056	0.1426	178.57	70.30		0.016	1085.958	331
36	0.005	0.127	200	78.74		0.0127	1360.892	414.8
37	0.0045	0.1131	222.22	87.49		0.01	1680.118	512.1
38	0.004	0.1007	250	98.43		0.00797	2127.953	648.6
39	0.0035	0.08969	285.71	112.48		0.00632	2781.496	847.8
40	0.0031	0.07987	322.58	127.00		0.00501	3543.307	1080

(*)insulation included

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 inch 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 millimeter, milliliter, and so-forth.

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

[edit] References

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.