Wire Gauge Chart

AWG is an acronym for American Wire Gauge (AWG). AWG sizes may be determined by measuring the diameter of the conductor with the insulation removed (the bare wire). Typically wire is chosen to suit how much amperage it is expected to carry over a certain distance (note that you can always use a thicker wire - lower gauge number - than recommended). As a side note, every 6 gauge decrease gives a doubling of the wire diameter (thickness), and every 3 gauge decrease doubles the wire cross sectional area.

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) (mm) (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 20.72 10.5       80/0.4
8 0.1285 3.264 7.78 3.06 16.52 8.37 2.2* 0.67* 40  
9 0.1144 2.906 8.74 3.44 13.08 6.63       >84/0.3
10 0.1019 2.588 9.81 3.86 10.38 5.26 3.2772 0.9989 30 <84/0.3
11 0.0907 2.305 11.03 4.34 8.23 4.17 4.1339 1.26   56/0.3
12 0.0808 2.053 12.38 4.87 6.53 3.31 5.21 1.588 20  
13 0.072 1.828 13.89 5.47 5.17 2.62 6.572 2.003   50/0.25
14 0.0641 1.628 15.6 6.14 4.10 2.08 8.284 2.525 15  
15 0.0571 1.45 17.51 6.89 3.26 1.65 10.45 3.184   >30/0.25
16 0.0508 1.291 19.69 7.75 2.59 1.31 13.18 4.016 10 <30/0.25
17 0.0453 1.15 22.08 8.69 2.05 1.04 16.614 5.064   32/0.2
18 0.0403 1.02362 24.81 9.77 1.62 0.823 20.948 6.385   >24/0.2
19 0.0359 0.9116 27.86 10.97 1.29 0.653 26.414 8.051   <24/0.2
20 0.032 0.8128 31.25 12.30 1.02 0.518 33.301 10.15   16/0.2
21 0.0285 0.7229 35.09 13.81 0.81 0.41 41.995 12.8    
22 0.0253 0.6438 39.53 15.56 0.64 0.326 52.953 16.14   7/0.25
23 0.0226 0.5733 44.25 17.42 0.51 0.258 66.798 20.36    
24 0.0201 0.5106 49.75 19.59 0.40 0.205 84.219 25.67   1/0.5, 7/0.2, 30/0.1
25 0.0179 0.4547 55.87 22.00 0.32 0.162 106.201 32.37    
26 0.0159 0.4049 62.89 24.76 0.255 0.129 133.891 40.81   7/0.15
27 0.0142 0.3606 70.42 27.72 0.201 0.102 168.865 51.47    
28 0.0126 0.3211 79.37 31.25 0.160 0.081 212.927 64.9    
29 0.0113 0.2859 88.5 34.84 0.127 0.0642 268.471 81.83    
30 0.01 0.2546 100 39.37 0.100 0.0509 338.583 103.2   1/0.25, 7/0.1
31 0.0089 0.2268 112.36 44.24 0.080 0.0404 426.837 130.1    
32 0.008 0.2019 125 49.21 0.063 0.032 538.386 164.1   1/0.2, 7/0.08
33 0.0071 0.1798 140.85 55.45 0.050 0.0254 678.806 206.9    
34 0.0063 0.1601 158.73 62.49 0.040 0.0201 833 260.9    
35 0.0056 0.1426 178.57 70.30 0.032 0.016 1085.958 331    
36 0.005 0.127 200 78.74 0.025 0.0127 1360.892 414.8    
37 0.0045 0.1131 222.22 87.49 0.020 0.01 1680.118 512.1    
38 0.004 0.1007 250 98.43 0.016 0.00797 2127.953 648.6    
39 0.0035 0.08969 285.71 112.48 0.012 0.00632 2781.496 847.8    
40 0.0031 0.07987 322.58 127.00 0.010 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 mm, 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 mm. 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.

WIRE GAUGE SELECTION TABLE
Example of use: a 12v circuit which is 15 feet long and is to carry 10 amps should use at least AWG #16 gauge wire.

Circuit Amperes

Circuit Watts

Wire gauge (for length in feet)

6V

12V

6V

12V

3'

5'

7'

10'

15'

20'

25'

0 to 2.5

0 to 5

15

30

18

18

18

18

18

18

18

3.0

6

18

36

18

18

18

18

18

18

16

3.5

7

21

42

18

18

18

18

18

18

16

4.0

8

24

48

18

18

18

18

18

16

16

5.0

10

30

60

18

18

18

18

16

16

16

5.5

11

33

66

18

18

18

18

16

16

14

6.0

12

36

72

18

18

18

18

16

16

14

7.5

15

45

90

18

18

18

18

14

14

12

9.0

18

54

108

18

18

16

16

14

14

12

10

20

60

120

18

18

16

16

14

12

10

11

22

66

132

18

18

16

16

12

12

10

12

24

72

144

18

18

16

16

12

12

10

15

30

90

180

18

16

16

14

10

10

10

20

40

120

240

18

16

14

12

10

10

8

25

50

150

300

16

14

12

12

10

10

8

50

100

300

600

12

12

10

10

6

6

4

75

150

450

900

10

10

8

8

4

4

2

100

200

600

1200

10

8

8

6

4

4

2

 

AWG - American Wire Gauge (also known as B&S - Browne & Sharpe)
SWG - Standard Wire Gauge (also known as BIS - British Imperial Standard)

Further charts can be found here
and here (Wikipedia)