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American wire gauge (AWG), also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used since 1857 predominantly in the United States and Canada for the diameters of round, solid, nonferrous, electrically conducting wire. The cross-sectional area of each gauge is an important factor for determining its current-carrying capacity.

The steel industry uses different wire gauges (for example, W&M Wire Gauge or US Steel Wire Gauge, or Music Wire Gauge). The table 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 gauge system originated in the number of drawing operations used to produce a given gauge of wire. Very fine wire (for example, 30 gauge) requires more passes through the drawing dies than does 0 gauge wire. Manufacturers of wire formerly had proprietary wire gauge systems; the development of standardized wire gauges rationalized selection of wire for a particular purpose.

The AWG tables are for a single, solid, round conductor. The AWG of a stranded wire is determined by the total cross-sectional area of the conductor, which determines its current-carrying capacity and electrical resistance. Because there are also small gaps between the strands, a stranded wire will always have a slightly larger overall diameter than a solid wire with the same AWG.

AWG is also commonly used to specify body piercing jewelry sizes, especially smaller sizes.

Formula

By definition, No. 36 AWG is 0.0050 inches in diameter, and No. 0000 is 0.4600 inches in diameter. The ratio of these diameters is 92, and there are 40 gauge sizes from No. 36 to No. 0000, or 39 steps. Using this common ratio, wire gauge sizes vary geometrically according to the following formula: The diameter of a No. n AWG wire is

or equivalently

The gauge can be calculated from the diameter using

^[3]

and the cross-section area is

,

Sizes with multiple zeros are successively larger than No. 0 and can be denoted using "number of zeros/0", for example 4/0 for 0000. For an m/0 AWG wire, use n = −(m−1) = 1−m in the above formulas. For instance, for No. 0000 or 4/0, use n = −3.

The ASTM B 258-02 standard defines the ratio between successive sizes to be the 39th root of 92, or approximately 1.1229322.^[4] ASTM B 258-02 also dictates that wire diameters should be tabulated with no more than 4 significant figures, with a resolution of no more than 0.0001 inches (0.1 mils) for wires larger than No. 44 AWG, and 0.00001 inches (0.01 mils) for wires No. 45 AWG and smaller.

Rules of thumb

The sixth power of this ratio is very close to 2, which leads to the following rules of thumb:

• When the diameter of a wire is doubled, the AWG will decrease by 6. (e.g., No. 2 AWG is about twice the diameter of No. 8 AWG.)
• When the cross-sectional area of a wire is doubled, the AWG will decrease by 3. (e.g., Two No. 14 AWG wires have about the same cross-sectional area as a single No. 11 AWG wire.)

Additionally, 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 a factor of approximately 10.

Table of AWG wire 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 with no insulation.

AWG	Diameter		Turns of wire		Area		Copper resistance		NEC copper wire ampacity with 60/75/ 90°C insulation (A)	Approximate stranded metric equivalents
	(inch)	(mm)	(per inch)	(per cm)	(kcmil)	(mm2)	(Ω/km)	(Ω/kFT)
0000 (4/0)	0.4600	11.684	2.17	0.856	212	107	0.1608	0.04901	195 / 230 / 260
000 (3/0)	0.4096	10.404	2.44	0.961	168	85.0	0.2028	0.06180	165 / 200 / 225
00 (2/0)	0.3648	9.266	2.74	1.08	133	67.4	0.2557	0.07793	145 / 175 / 195
0 (1/0)	0.3249	8.252	3.08	1.21	106	53.5	0.3224	0.09827	125 / 150 / 170
1	0.2893	7.348	3.46	1.36	83.7	42.4	0.4066	0.1239	110 / 130 / 150
2	0.2576	6.544	3.88	1.53	66.4	33.6	0.5127	0.1563	95 / 115 / 130
3	0.2294	5.827	4.36	1.72	52.6	26.7	0.6465	0.1970	85 / 100 / 110	196/0.4
4	0.2043	5.189	4.89	1.93	41.7	21.2	0.8152	0.2485	70 / 85 / 95
5	0.1819	4.621	5.50	2.16	33.1	16.8	1.028	0.3133		126/0.4
6	0.1620	4.115	6.17	2.43	26.3	13.3	1.296	0.3951	55 / 65 / 75
7	0.1443	3.665	6.93	2.73	20.8	10.5	1.634	0.4982		80/0.4
8	0.1285	3.264	7.78	3.06	16.5	8.37	2.061	0.6282	40 / 50 / 55
9	0.1144	2.906	8.74	3.44	13.1	6.63	2.599	0.7921		84/0.3
10	0.1019	2.588	9.81	3.86	10.4	5.26	3.277	0.9989	30 / 35 / 40
11	0.0907	2.305	11.0	4.34	8.23	4.17	4.132	1.260		56/0.3
12	0.0808	2.053	12.4	4.87	6.53	3.31	5.211	1.588	25 / 25 / 30 (20)
13	0.0720	1.828	13.9	5.47	5.18	2.62	6.571	2.003		50/0.25
14	0.0641	1.628	15.6	6.14	4.11	2.08	8.286	2.525	20 / 20 / 25 (15)
15	0.0571	1.450	17.5	6.90	3.26	1.65	10.45	3.184		30/0.25
16	0.0508	1.291	19.7	7.75	2.58	1.31	13.17	4.016	— / — / 18 (10)
17	0.0453	1.150	22.1	8.70	2.05	1.04	16.61	5.064		32/0.2
18	0.0403	1.024	24.8	9.77	1.62	0.823	20.95	6.385	— / — / 14 (7)	24/0.2
19	0.0359	0.912	27.9	11.0	1.29	0.653	26.42	8.051
20	0.0320	0.812	31.3	12.3	1.02	0.518	33.31	10.15		16/0.2
21	0.0285	0.723	35.1	13.8	0.810	0.410	42.00	12.80		13/0.2
22	0.0253	0.644	39.5	15.5	0.642	0.326	52.96	16.14		7/0.25
23	0.0226	0.573	44.3	17.4	0.509	0.258	66.79	20.36
24	0.0201	0.511	49.7	19.6	0.404	0.205	84.22	25.67		1/0.5, 7/0.2, 30/0.1
25	0.0179	0.455	55.9	22.0	0.320	0.162	106.2	32.37
26	0.0159	0.405	62.7	24.7	0.254	0.129	133.9	40.81		7/0.15
27	0.0142	0.361	70.4	27.7	0.202	0.102	168.9	51.47
28	0.0126	0.321	79.1	31.1	0.160	0.0810	212.9	64.90
29	0.0113	0.286	88.8	35.0	0.127	0.0642	268.5	81.84
30	0.0100	0.255	99.7	39.3	0.101	0.0509	338.6	103.2		1/0.25, 7/0.1
31	0.00893	0.227	112	44.1	0.0797	0.0404	426.9	130.1
32	0.00795	0.202	126	49.5	0.0632	0.0320	538.3	164.1		1/0.2, 7/0.08
33	0.00708	0.180	141	55.6	0.0501	0.0254	678.8	206.9
34	0.00630	0.160	159	62.4	0.0398	0.0201	856.0	260.9
35	0.00561	0.143	178	70.1	0.0315	0.0160	1079	329.0
36	0.00500	0.127	200	78.7	0.0250	0.0127	1361	414.8
37	0.00445	0.113	225	88.4	0.0198	0.0100	1716	523.1
38	0.00397	0.101	252	99.3	0.0157	0.00797	2164	659.6
39	0.00353	0.0897	283	111	0.0125	0.00632	2729	831.8
40	0.00314	0.0799	318	125	0.00989	0.00501	3441	1049

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. Some common cables are midway between two AWG sizes. 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 circle with 1000 mil = 1 inch diameter. An older abbreviation for one thousand circular mils is MCM.

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.

Note that the area in mm² may differ somewhat from the numbers given in the table, depending on number of strands etc.

Pronunciation

AWG is colloquially referred to as gauge and the zeros in large wire sizes are referred to as aught (pronounced /ˈɔːt/). Wire sized 1 AWG is referred to as "one gauge"; similarly, smaller diameters are pronounced "x gauge", where x is the positive integer AWG number. Larger wire (#0 and up) is referred to as "one aught", "two aught" etc., depending on how many zeros are in the AWG rating.