American wire gauge

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.

Formulas

By definition, No. 36 AWG is 0.005 inches diameter, and No. 0000 is 0.46 inches diameter. The diameter increases by 0.46/0.005 = 92 times, evenly divided into 39 sizes. 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.

The ratio between successive sizes is the 39th root of 92, or approximately 1.1229322. [1]

The sixth power of this ratio is nearly 2.0, 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.

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 operation of the wires and does not take skin effect into account.

AWG	Diameter		Area	Copper resistance	Copper resistance[2]	Copper wire current rating with 60 °C insulation	Approximate stranded metric equivalents
	(in)	(mm)	(mm²)	(Ω/1 km)	(Ω/1000 ft)	(A)
000000(6/0)	0.5800	14.73	170
00000(5/0)	0.5165	13.12	135
0000(4/0)	0.4600	11.68	107
000(3/0)	0.4096	10.40	85
00(2/0)	0.3648	9.266	67.4
0(1/0)	0.3249	8.251	53.5		~0.1
1	0.2893	7.348	42.4			110
2	0.2576	6.544	33.6			95
3	0.2294	5.827	26.7			85	196/0.4
4	0.2043	5.189	21.2			70
5	0.1819	4.621	16.8				126/0.4
6	0.1620	4.115	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		0.9989	30	<84/0.3
11	0.0907	2.305	4.17		1.260		56/0.3
12	0.0808	2.053	3.31		1.588	20
13	0.0720	1.828	2.62		2.003		50/0.25
14	0.0641	1.628	2.08		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		5.064		32/0.2
18	0.0403	1.024	0.823		6.385		>24/0.2
19	0.0359	0.9116	0.653		8.051		<24/0.2
20	0.0320	0.8118	0.518		10.15		16/0.2
21	0.0285	0.7229	0.410		12.80
22	0.0253	0.6438	0.326		16.14		7/0.25
23	0.0226	0.5733	0.258		20.36
24	0.0201	0.5106	0.205		25.67		1/0.5, 7/0.2, 30/0.1
25	0.0179	0.4547	0.162		32.37
26	0.0159	0.4049	0.129		40.81		7/0.15
27	0.0142	0.3606	0.102		51.47
28	0.0126	0.3211	0.081		64.90
29	0.0113	0.2859	0.0642	268.5	81.83
30	0.0100	0.2546	0.0509		103.2		1/0.25, 7/0.1
31	0.0089	0.2268	0.0404		130.1
32	0.0080	0.2019	0.0320		164.1		1/0.2, 7/0.08
33	0.0071	0.1798	0.0254		206.9
34	0.0063	0.1601	0.0201		260.9
35	0.0056	0.1426	0.0160		331.0
36	0.0050	0.1270	0.0127		414.8
37	0.0045	0.1131	0.0100		512.1
38	0.0040	0.1007	0.00797		648.6
39	0.0035	0.08969	0.00632		847.8
40	0.0031	0.07987	0.00501		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.

1. ^ Bare, solid copper wire at 68 °F — Resistance data is from Belden Master Catalog, 1995.

Reference

• Donald G. Fink and H. Wayne Beaty, Standard Handbook for Electrical Engineers, Eleventh Edition,McGraw-Hill, New York, 1978, ISBN 007020974X, page 4-18 and table 4-11.

See also

• IEC 60228 for international standard wire sizes
• Imperial Wire Gauge & British Standard Gauge
• Wikimedia chart comparing all known wire gauges to each other.

External links

• How to Gauge Traces