Industry Information

American wire gauge

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 does not use AWG and prefers a number of other wire gauges. These include Washburn & Moen (or W&M) Wire Gauge, US Steel Wire Gauge, and Music Wire Gauge.

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) required more passes through the drawing dies than did 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), even when the material is not metallic. 

The ASTM B 258-02 standard defines the ratio between successive sizes to be the 39th root of 92, or approximately 1.1229322. 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.

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.

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.

Aluminum wire has a conductivity of approximately 61% of copper, so an aluminum wire has the almost same resistance as a copper wire 2 AWG smaller. (Which has 62.9% of the area.)

Tables 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. Fusing Current (merlting wire) is estimated based on 25°C ambient temperature. 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 an upper limit for wire with no insulation.

AWG

Diameter

Turns of wire
(no insulation)

Area

Copper
resistance
[6]

NEC copper wire
ampacity with
60/75/90 °C
insulation (A)
[7]

Approximate
standard metric
equivalents

Fusing Current (copper)

(inch)

(mm)

(per in)

(per cm)

(kcmil)

(mm2)

(Ω/km)
(mΩ/m)

(Ω/kFT)
(mΩ/ft)

Preece
(~10s)

Onderdonk
(1s)

Onderdonk
(32ms)

0000 (4/0)

0.4600

11.684

2.17

0.856

212

107

0.1608

0.04901

195 / 230 / 260

 

 

31 kA

173 kA

000 (3/0)

0.4096

10.404

2.44

0.961

168

85.0

0.2028

0.06180

165 / 200 / 225

 

 

24.5 kA

137 kA

00 (2/0)

0.3648

9.266

2.74

1.08

133

67.4

0.2557

0.07793

145 / 175 / 195

 

 

19.5 kA

109 kA

0 (1/0)

0.3249

8.252

3.08

1.21

106

53.5

0.3224

0.09827

125 / 150 / 170

 

1.9 kA

15.5 kA

87 kA

1

0.2893

7.348

3.46

1.36

83.7

42.4

0.4066

0.1239

110 / 130 / 150

 

1.6 kA

12 kA

68 kA

2

0.2576

6.544

3.88

1.53

66.4

33.6

0.5127

0.1563

95 / 115 / 130

 

1.3 kA

9.7 kA

54 kA

3

0.2294

5.827

4.36

1.72

52.6

26.7

0.6465

0.1970

85 / 100 / 110

196/0.4

1.1 kA

7.7 kA

43 kA

4

0.2043

5.189

4.89

1.93

41.7

21.2

0.8152

0.2485

70 / 85 / 95

 

946 A

6.1 kA

34 kA

5

0.1819

4.621

5.50

2.16

33.1

16.8

1.028

0.3133

 

126/0.4

795 A

4.8 kA

27 kA

6

0.1620

4.115

6.17

2.43

26.3

13.3

1.296

0.3951

55 / 65 / 75

 

668 A

3.8 kA

21 kA

7

0.1443

3.665

6.93

2.73

20.8

10.5

1.634

0.4982

 

80/0.4

561 A

3 kA

17 kA

8

0.1285

3.264

7.78

3.06

16.5

8.37

2.061

0.6282

40 / 50 / 55

 

472 A

2.4 kA

13.5 kA

9

0.1144

2.906

8.74

3.44

13.1

6.63

2.599

0.7921

 

84/0.3

396 A

1.9 kA

10.7 kA

10

0.1019

2.588

9.81

3.86

10.4

5.26

3.277

0.9989

30 / 35 / 40

333 A

1.5 kA

8.5 kA

11

0.0907

2.305

11.0

4.34

8.23

4.17

4.132

1.260

 

56/0.3

280 A

1.2 kA

6.7 kA

12

0.0808

2.053

12.4

4.87

6.53

3.31

5.211

1.588

25 / 25 / 30

 

235 A

955 A

5.3 kA

13

0.0720

1.828

13.9

5.47

5.18

2.62

6.571

2.003

 

50/0.25

198 A

758 A

4.2 kA

14

0.0641

1.628

15.6

6.14

4.11

2.08

8.286

2.525

20 / 20 / 25

64/0.2

166 A

601 A

3.3 kA

15

0.0571

1.450

17.5

6.90

3.26

1.65

10.45

3.184

 

30/0.25

140 A

477 A

2.7 kA

16

0.0508

1.291

19.7

7.75

2.58

1.31

13.17

4.016

— / — / 18

117 A

377 A

2.1 kA

17

0.0453

1.150

22.1

8.70

2.05

1.04

16.61

5.064

 

32/0.2

99 A

300 A

1.7 kA

18

0.0403

1.024

24.8

9.77

1.62

0.823

20.95

6.385

— / — / 14

24/0.2

83 A

237 A

1.3 kA

19

0.0359

0.912

27.9

11.0

1.29

0.653

26.42

8.051

 

70 A

189 A

1 kA

20

0.0320

0.812

31.3

12.3

1.02

0.518

33.31

10.15

 

16/0.2

58.5 A

149 A

834 A

21

0.0285

0.723

35.1

13.8

0.810

0.410

42.00

12.80

 

13/0.2

49 A

119 A

662 A

22

0.0253

0.644

39.5

15.5

0.642

0.326

52.96

16.14

 

7/0.25

41 A

94 A

525 A

23

0.0226

0.573

44.3

17.4

0.509

0.258

66.79

20.36

 

 

35 A

74 A

416 A

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

29 A

59 A

330 A

25

0.0179

0.455

55.9

22.0

0.320

0.162

106.2

32.37

 

 

24 A

47 A

262 A

26

0.0159

0.405

62.7

24.7

0.254

0.129

133.9

40.81

 

1/0.4, 7/0.15

20 A

37 A

208 A

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

 

7/0.12

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

 

 


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. The next wire size larger than 4/0 has a cross section of 250 kcmil. 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.

Stranded wire AWG sizes

AWG gauges are also used to describe stranded wire. In this case, it describes the total cross-sectional area of the conductor; the gaps between strands are not counted. Using circular strands, these gaps occupy about 10% of the wire area, thus requiring a wire about 5% thicker than equivalent solid wire.

Stranded wires are specified with three numbers, the overall AWG size, the number of strands, and the AWG size of a strand. The number of strands and the AWG of a strand are separated by a slash. For example, a 22 AWG 7/30 stranded wire is a 22 AWG wire made from seven strands of 30 AWG wire.

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