American wire gauge

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American wire gauge (AWG) tells the diameter of an electrical conductor. A conductor's current capacity depends upon the resistance per unit length and the temperature rating of the insulation. Wire type THHN is rated at 90 °C, and it has an added nylon jacket.

Electric welders use a lot of current for short periods. The National Electrical Code (NEC) provides for welders by allowing wire size of only half the capacity that would otherwise be required. For example, a 50 amp circuit breaker, a 50 amp outlet, but only 10 AWG wire.

A similar exception is made for protective ground wires, which can have only half the capacity of the current carrying conductors.

Tables of AWG wire sizes[edit]

Most of the following table came from Wikipedia. Diameter and turns apply only to solid wire. The total diameter of stranded wire is larger than solid, even though the conductive cross sections are the same.

AWG Diameter
(of solid wire)
Turns of wire,
without insulation
(with solid wire)
Area Copper wire
Resistance/length Ampacity
60 °C 75 °C 90 °C
(in) (mm) (per in) (per cm) (kcmil) (mm2) (mΩ/m (mΩ/ft (A)
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 10.405 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 8.251 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 110 130 145
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 85 100 115
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
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
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
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
12 0.0808 2.053 12.4 4.87 6.53 3.31 5.211 1.588 20 25 30
13 0.0720 1.828 13.9 5.47 5.18 2.62 6.571 2.003
14 0.0641 1.628 15.6 6.14 4.11 2.08 8.286 2.525 15 20 25
15 0.0571 1.450 17.5 6.90 3.26 1.65 10.45 3.184
16 0.0508 1.291 19.7 7.75 2.58 1.31 13.17 4.016 22*free air 13*enclosed 18
17 0.0453 1.150 22.1 8.70 2.05 1.04 16.61 5.064
18 0.0403 1.024 24.8 9.77 1.62 0.823 20.95 6.385 10 14 16
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 7.5 11
21 0.0285 0.723 35.1 13.8 0.810 0.410 42.00 12.80
22 0.0253 0.644 39.5 15.5 0.642 0.326 52.96 16.14 7 5
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 3.5 2.1
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 2.2 1.3
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 1.4 0.85
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 0.86 0.52
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 0.53 0.3
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 0.3 0.180
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

Number of wires in conduit[edit]

National Electrical Code Article 348-6 limits the total cross sectional area of wires to a certain percentage of the cross sectional area of a conduit.

Allowable fill
Conductors Percent filled
1 53
2 31
3 or more 40


For type THHN wire installed in standard EMT conduits, allowable fill works out to:

Maximum THHN conductors in a conduit
AWG 12 34 1 1 14 1 12
14 13 24 39 69 94
12 10 18 29 51 70
10 6 11 18 32 44
8 3 5 9 16 22
6 1 4 6 11 15
4 1 2 4 7 9

Number of conductors in a box[edit]

Article 370-6 limits the number of conductors entering a box. A conductor that passes through a box, without any connection, counts as one conductor. A conductor that begins and ends within a box is not counted at all. The size of devices, such as outlets and switches, must be subtracted from the capacity of the box.

Capacity of selected box sizes
Box type Cubic inches 14 12 10 8 6
4 x 1 14 Round 12.5 6 5 5 4 0
4 x 1 14 Square 18.0 9 8 7 6 0
4 x 1 12 Square 21.0 10 9 8 7 0
4 x 2 18 Square 30.3 15 13 12 10 6
4 1116 x 2 18 Square 42.0 21 18 16 14 6