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AWG

AWG (American Wire Gauge) – is an American standardized system for determining diameters or cross-sectional areas of wires.

 

AWG is expressed as integer value (e.g. 1, 2 or 15) corresponding to a specific dimension (in mm, inches, mm2 or kcmil). Within this system, increasing gauge numbers denote decreasing wire size.
Example: 1 AWG = 42.40 mm2, whereas 28 AWG = 0.32 mm2.

 

Fig. 1. Approximate ratio (in a suitable scale) of different wire sizes in AWG standard

 

AWG standard has been developed at the beginning of the 19th century, with its final version developed in 1957 by Joseph Rogers Brown for Browne & Sharpe - a manufacturer of measuring instruments. AWG is also called Brown and Sharpe wire gauge (B&S).

The inverse order of the AWG is due to the wire production process used at the time the system has been developed. At first, AWG corresponded to the number of drawing operations used to produce a given gauge of wire on the drawing die. A blank with a 160 kcmil cross-sectional area requires 20 drawing operations through successively smaller dies to reach the desired size - a wire with a 1.02 kcmil (20 AWG) cross-sectional area. The gauges below one (0 [1/0], 00 [2/0], 000 [3/0] and 0000 [4/0]) has been introduced at a later date, and the wires with corresponding dimensions were manufactured from blanks, compacts or cast rods with cross-sectional area over 106 kcmil.

 

Fig. 2. Changes in gauge number after a single draw of the wire through each die: (a) initial wire, (b) to (d) subsequent gauge wires. Example: (a) = 6 AWG → (e) = 10 AWG

 

There are 44 gauge sizes: from No. 0000 [4/0] corresponding to the largest wire diameter to No. 40 corresponding to the smallest wire diameter. Each successive gauge number increases cross-sectional area by approx. 20.5% and diameter by approx. 10.25%. The drawing dies used by Brown & Sharpe allowed to reduce the wire diameter by exactly 10.25%.

It leads to the following:
– when the cross-sectional area is doubled, the gauge will decrease by 3, e.g. two No. 12 AWG has the same cross-sectional area as a single No. 9 AWG wire;
– when the diameter of a wire is doubled, the gauge will decrease by 6, e.g. No. 9 AWG wire is about twice the diameter of No. 15 AWG wire;
– when the diameter of a wire is tripled, the gauge will decrease by 10;
– when the diameter of a wire is increased fivefold, the gauge will decrease by 14;
– when the diameter of a wire is increased tenfold, the gauge will decrease by 20.

Physical properties of the wire materials also impose certain rules. Aluminium wire has a conductivity of approx. 61% of copper. The aluminium wires has the same resistance as a copper wire smaller by 2 AWG sizes.

 

An accurate wire diameter (in mm) for a specific AWG size may be expressed as follows:

 

and

 

or in inches:

 

and

 

where:
d – diameter,
n – AWG size.

 

Table 1 shows dimensions and basic physical properties of the various wire gauges.

 

Table 1. American Wire Gauge (AWG) – dimensions, resistances and maximum ampacity (DC) and a maximum frequency at which the skin effect does not occur (AC). All parameters are based on a copper wire at 25°C

 

AWG Diameter Cross-sectional area Resistance Maximum ampacity as: Maximum frequency for skin depth = 100% area
mm inch mm² kcmil Ω/km Ω/kft GND [A] power supply [A]
0000
[4/0]
11.684 0.4600 107 212 0.1608 0.04901 380 302 125 Hz
000
[3/0]
10.404 0.4096 85 168 0.2028 0.06180 328 239 160 Hz
00
[2/0]
9.266 0.3648 67.4 133 0.2557 0.07793 283 190 200 Hz
0
[1/0]
8.252 0.3249 53.5 106 0.3224 0.09827 245 150 250 Hz
1 7.348 0.2893 42.4 83.7 0.4066 0.1239 211 119 325 Hz
2 6.544 0.2576 33.6 66.4 0.5127 0.1563 181 94 410 Hz
3 5.827 0.2294 26.7 52.6 0.6465 0.1970 158 75 500 Hz
4 5.189 0.2043 21.2 41.7 0.8152 0.2485 135 60 650 Hz
5 4.621 0.1819 16.8 33.1 1.028 0.3133 118 47 810 Hz
6 4.115 0.1620 13.3 26.3 1.296 0.3951 101 37 1100 Hz
7 3.665 0.1443 10.5 20.8 1.634 0.4982 89 30 1300 Hz
8 3.264 0.1285 8.37 16.5 2.061 0.6282 73 24 1650 Hz
9 2.906 0.1144 6.63 13.1 2.599 0.7921 64 19 2050 Hz
10 2.588 0.1019 5.26 10.4 3.277 0.9989 55 15 2600 Hz
11 2.305 0.0907 4.17 8.23 4.132 1.260 47 12 3200 Hz
12 2.053 0.0808 3.31 6.53 5.211 1.588 41 9.3 4150 Hz
13 1.828 0.0720 2.62 5.18 6.571 2.003 35 7.4 5300 Hz
14 1.628 0.0641 2.08 4.11 8.286 2.525 32 5.9 6700 Hz
15 1.450 0.0571 1.65 3.26 10.45 3.184 28 4.7 8250 Hz
16 1.291 0.0508 1.31 2.58 13.17 4.016 22 3.7 11 kHz
17 1.150 0.0453 1.04 2.05 16.61 5.064 19 2.9 13 kHz
18 1.024 0.0403 0.823 1.62 20.95 6.385 16 2.3 17 kHz
19 0.912 0.0359 0.653 1.29 26.42 8.051 14 1.8 21 kHz
20 0.812 0.0320 0.518 1.02 33.31 10.15 11 1.5 27 kHz
21 0.723 0.0285 0.410 0.810 42.00 12.80 9 1.2 33 kHz
22 0.643 0.0253 0.326 0.642 52.96 16.14 7 0.92 42 kHz
23 0.573 0.0226 0.258 0.509 66.79 20.36 4.7 0.73 53 kHz
24 0.511 0.0201 0.205 0.404 84.22 25.67 3.5 0.58 68 kHz
25 0.455 0.0179 0.162 0.320 106.2 32.37 2.7 0.46 85 kHz
26 0.405 0.0159 0.129 0.254 133.9 40.81 2.2 0.36 107 kHz
27 0.361 0.0142 0.102 0.202 168.9 51.47 1.7 0.29 130 kHz
28 0.321 0.0126 0.0810 0.160 212.9 64.9 1.4 0.23 170 kHz
29 0.286 0.0113 0.0642 0.127 268.5 81.84 1.2 0.18 210 kHz
30 0.255 0.0100 0.0509 0.101 338.6 103.2 0.86 0.14 270 kHz
31 0.227 0.00893 0.0404 0.0797 426.9 130.1 0.70 0.11 340 kHz
32 0.202 0.00795 0.0320 0.0632 538.3 164.1 0.53 0.09 430 kHz
33 0.180 0.00708 0.0254 0.0501 678.8 206.9 0.43 0.07 540 kHz
34 0.160 0.00630 0.0201 0.0398 856.0 260.9 0.33 0.06 690 kHz
35 0.143 0.00561 0.0160 0.0315 1079 329.0 0.27 0.04 870 kHz
36 0.127 0.00500 0.0127 0.0250 1361 414.8 0.21 0.04 1100 kHz
37 0.113 0.00445 0.0100 0.0198 1716 523.1 0.17 0.03 1350 kHz
38 0.101 0.00397 0.00797 0.0157 2164 659.6 0.13 0.02 1750 kHz
39 0.0897 0.00353 0.00632 0.0125 2729 831.8 0.11 0.02 2250 kHz
40 0.0799 0.00314 0.00501 0.00989 3441 1049 0.09 0.01 2900 kHz

Diameters of solid wires and stranded wires of the same AWG size are different, since the diameter/cross-sectional area determines the AWG wire size. Cross-sectional area/diameter of the stranded wire includes wires and gaps between the wires. The gaps depend on the wire layout within the round stranded wire. The AWG gauge of a stranded wire represents the sum of the cross-sectional areas of the individual wires, and not the cross-sectional area of the stranded wire as a whole.

Table 2 shows parameters of a solid wire and a stranded wire. Layout, outer diameter and cross-sectional area (including gaps between wires – not including insulation) and wire resistance (in Ω/km) are compared.

 

Table 2. Comparison of basic parameters of solid wires and stranded wires (n – number of wires)

 

AWG Wire layout Diameter Cross-sectional area Resistance
n/AWG n x mm mm mm² Ω/km
0000
[4/0]
Single solid wire 11.684 107 0.16
259/21 259 x 0.724 13.259 106.63 0.16
427/23 427 x 0.574 13.259 110.49 0.15
000
[3/0]
Single solid wire 10.405 85.0 0.20
259/22 259 x 0.643 11.786 84.40 0.20
427/24 427 x 0.511 11.786 87.57 0.19
00
[2/0]
Single solid wire 9.266 67.4 0.25
133/20 133 x 0.813 10.516 69.04 0.25
259/23 259 x 0.574 10.516 67.02 0.25
0
[1/0]
Single solid wire 8.251 53.5 0.32
133/21 133 x 0.724 9.347 54.75 0.31
259/24 259 x 0.511 9.347 53.12 0.32
1 Single solid wire 7.348 42.4 0.40
133/22 133 x 0.643 8.331 43.19 0.40
259/25 259 x 0.045 8.331 42.11 0.41
817/30 817 x 0.254 8.331 41.40 0.42
2109/36 2109 x 0.160 8.331 42.40 0.41
2 Single solid wire 6.544 33.60 0.51
133/23 133 x 0.574 7.417 34.42 0.50
259/26 259 x 0.404 7.417 33.20 0.52
665/30 665 x 0.256 7.417 33.70 0.52
2646/36 2646 x 0.127 7.417 33.52 0.52
4 Single solid wire 5.189 21.20 0.82
133/225 133 x 0.455 5.898 21.63 0.80
259/27 259 x 0.363 5.898 26.80 0.66
1666/36 1666 x 0.127 5.898 21.10 0.82
6 Single solid wire 4.115 13.30 1.29
133/27 133 x 0.363 4.674 13.76 1.50
259/30 259 x 0.254 4.674 13.12 1.30
1050/36 1050 x 0.127 4.674 13.32 1.30
8 Single solid wire 3.264 8.37 2.06
49/25 49 x 0.455 3.734 7.96 2.20
133/29 133 x 0.287 3.734 8.60 2.00
655/36 655 x 0.127 3.734 8.30 2.00
10 Single solid wire 2.588 5.26 3.27
37/26 37 x 0.404 2.921 4.74 3.60
49/27 49 x 0.363 2.946 5.07 3.60
105/30 105 x 0.254 2.946 5.32 3.20
12 Single solid wire 2.053 3.21 5.21
7/20 7 x 0.813 2.438 3.63 4.80
19/25 19 x 0.455 2.369 3.09 5.60
65/30 65 x 0.254 2.413 3.29 5.70
165/34 165 x 0.160 2.413 3.32 5.20
14 Single solid wire 1.628 2.08 8.28
7/22 7 x 0.643 1.854 2.238 7.60
19/27 19 x 0.361 1.854 1.945 8.90
41/30 41 x 0.254 1.854 2.078 8.30
105/34 105 x 0.160 1.854 2.111 8.20
16 Single solid wire 1.291 1.310 13.2
7/24 7 x 0.511 1.524 1.440 12.0
19/29 19 x 0.287 1.473 1.229 14.0
26/30 26 x 0.254 1.499 1.317 13.1
65/34 65 x 0.160 1.499 1.310 13.2
105/36 105 x 0.127 1.499 1.330 13.1
18 Single solid wire 1.024 0.823 21.0
7/26 7 x 0.404 1.219 0.897 19.2
16/30 16 x 0.254 1.194 0.811 21.3
19/30 19 x 0.254 1.245 0.963 17.9
41/34 41 x 0.160 1.194 0.824 20.9
65/36 65 x 0.127 1.194 0.823 21.0
20 Single solid wire 0.812 0.518 33.3
7/28 7 x 0.320 0.865 0.562 33.8
10/30 10 x 0.254 0.889 0.507 33.9
19/32 19 x 0.203 0.940 0.615 28.3
26/34 26 x 0.160 0.914 0.523 33.0
41/36 41 x 0.127 0.914 0.520 32.9
22 Single solid wire 0.644 0.326 53.0
7/30 7 x 0.254 0.762 0.355 48.4
19/34 19 x 0.160 0.787 0.382 45.1
26/36 26 x 0.127 0.762 0.330 52.3
24 Single solid wire 0.511 0.205 84.2
7/32 7 x 0.203 0.610 0.227 76.4
10/34 10 x 0.160 0.582 0.201 85.6
19/36 19 x 0.127 0.610 0.241 69.2
41/40 41 x 0.078 0.582 0.196 84.0
26 Single solid wire 0.405 0.129 133.9
7/34 7 x 0.160 0.483 0.141 122.0
19/38 19 x 0.102 0.508 0.155 113.0
10/36 10 x 0.127 0.533 0.127 137.0
28 Single solid wire 0.321 0.081 212.9
7/36 7 x 0.127 0.381 0.087 213.0
19/40 19 x 0.078 0.406 0.091 186.0
30 Single solid wire 0.255 0.050 338.6
7/38 7 x 0.102 0.305 0.057 339.0
19/42 19 x 0.064 0.305 0.061 286.7
32 Single solid wire 0.202 0.032 538.3
7/40 7 x 0.078 0.203 0.034 538.0
19/44 19 x 0.050 0.229 0.037 448.0
34 Single solid wire 0.160 0.020 856.0
7/42 7 x 0.064 0.192 0.022 777.0
36 Single solid wire 0.127 0.013 1362.0
7/44 7 x 0.050 0.152 0.014 1271.0

The table shows a list of AWG sizes from 4/0 [No. 0000] to No. 2 and successive even AWG sizes up to No. 36 incl. Wires with AWG size over 36 are not available as stranded wires, since the wire diameter required would have to be extremely small.

 

AWG has been developed and initially used in the USA. It is now widely used worldwide, replacing other systems and standards. It has competed with a British Birmingham Wire Gauge (BWG) system, however, at the end of the 19th century, slightly modified BWG has been replaced by Standard Wire Gauge (SWG), now widely used in the UK. SWG is also known as Imperial Wire Gauge or British Standard Gauge. SWG gauges look almost identical to AWG gauges, however the sizes correspond to different wire dimensions.

 

Fig. 3. Comparison of AWG (left) and SWG (right) wire gauges. No. 14 AWG ≈ No. 16 SWG

 

Fig. 3 shows No. 14 AWG as nearly equal to No. 16 SWG.

The main difference between AWG and SWG is the material of the wire. The American system has been developed to measure solid and stranded wires made of metals and non-ferrous alloys (non-magnetic) - mainly copper, but also aluminium or silver. The British standard has been developed to standardize the sizes of ferrous wires. There are 44 basic AWG gauge sizes and 57 SWG gauge sizes.

Standard Wire Gauge has been gradually withdrawn and replaced by BS 6722:1986.

 

AWG is commonly used in the manufacturing of different wire types in countries using the imperial system of measurements. In countries using the metric system, both BS 6722:1986 and AWG are used depending on the application of the manufactured wire.

 

Fig. 4. Example wires manufactured to AWG and BS 6722:1986 include (a) HDMI, (b) USB, (c) 5 V and 12 V cables from power supply to PC, (d) power supply cable with IEC-C5 connector

 

The technical specifications included in the standards for data transmission or power supply interfaces include strict guidelines for manufacturing compatible cables. Considering that a majority of new technologies is still being developed in the USA (or in close cooperation with US companies), the wires used in electronic devices are mainly manufactured to AWG standards.

The computer networks use UTP and FTP cables, with a single strand diameter between No. 22 AWG and No. 24 AWG. For short sections, patch cords with No. 26 AWG strands can be used.

For HDMI – HDMI Working Group interface (developer of the standard) it is recommended that Standard HDMI Cable are made of No. 28 AWG strands, High Speed HDMI Cable are made of No. 24 AWG strands. The guidelines are not specified for Premium High Speed HDMI Cable.

In practice, AWG size depends on the cable length:
– cables up to 3 m long require No. 30–28 AWG gauges,
– cables 3 m to 10 m long require No. 28–26 AWG gauges,
– cables over 10 m long – No. 26 AWG or lower gauges.

 

When connecting the devices transmitting a high volume of data (e.g. BluRay 3D or high-end graphics cards) to the receivers using 4K or higher resolution, it is recommended to use the shortest cables with the lowest AWG size possible.

 

For USB standard, two cable types are manufactured:
– for data transmission between external devices (digital cameras, storage devices with external power supply etc.) and the PC – cables with a single size strands, usually No. 28 AWG;
– for power supply – double AWG size marking (see Fig. 4b) – separate for D- and D+ (No. 28 AWG) and power supply and GND – usually No. 24 AWG.

 

As per the standard specification, power supply from USB should have a voltage of 5 V with ±5% (0.25 V) tolerance. USB supplied device (keyboard, portable HDD, internet camera etc.) should continue to operate at voltage drop between 0.55 V and 4.45 V (for USB 2.0) or between 0.6 V to 4.4 V (for USB 3.0).

 

The following tables (Table 3a–3d) show 5V voltage drop depending on strand diameter and wire length. The tables below show currents for the most popular USB chargers for mobile and portable devices: Table 3a - older phones; Table 3b, Table 3c and Table 3d – smartphones, tablets etc.

 

Table 3a. Power supply – 500 mA

 

AWG 15 cm 50 cm 1 m 2 m 3 m 5 m
20 0.064 0.076 0.093 0.126 0.159 0.226
22 0.067 0.086 0.112 0.165 0.218 0.324
24 0.072 0.102 0.144 0.228 0.312 0.481
26 0.080 0.126 0.193 0.327 0.461 0.729
28 0.091 0.166 0.272 0.485 0.698 1.124

Table 3b. Power supply – 1000 mA

 

AWG 15 cm 50 cm 1 m 2 m 3 m 5 m
20 0.129 0.153 0.186 0.253 0.319 0.453
22 0.125 0.172 0.225 0.331 0.437 0.649
24 0.145 0.204 0.288 0.456 0.625 0.962
26 0.160 0.253 0.387 0.655 0.923 1.459
28 0.183 0.332 0.545 0.971 1.397 2.249

Table 3c. Power supply – 2000 mA

 

AWG 15 cm 50 cm 1 m 2 m 3 m 5 m
20 0.259 0.306 0.373 0.506 0.639 0.906
22 0.271 0.345 0.451 0.663 0.875 1.299
24 0.290 0.408 0.576 0.913 1.250 1.924
26 0.320 0.507 0.775 1.311 1.846 2.918
28 0.367 0.665 1.091 1.943 2.794 4.498

Table 3d. Power supply – 2400 mA

 

AWG 15 cm 50 cm 1 m 2 m 3 m 5 m
20 0.311 0.367 0.447 0.607 0.767 1.087
22 0.326 0.415 0.542 0.796 1.050 1.559
24 0.348 0.490 0.692 1.096 1.500 2.309
26 0.384 0.609 0.930 1.573 2.216 3.501
28 0.412 0.798 1.309 2.331 3.353 5.397

The colours indicate supply voltage drop: 

Green - supply voltage drop up to 4.75 V
Yellow - 4.75 V to 4.45 V
Yellow-red - 4.45 V to 4.4 V
Red - below 4.4 V

The values were calculated based on the Ohm’s law, allowing for the copper conductor and USB port resistance (approx. 30 mΩ).

The combinations of AWG size and cable length conforming to the voltage standard specification at the power supply cable output are marked green.

The combinations of AWG size and cable length for charge a smartphone are marked yellow (yellow-red for USB 3.0). The voltage drops below the voltage specified in the USB specification for charging devices (for a charger), and is maintained within the limits required for charged devices (e.g. tablet).

The cables that should not be used to charge USB devices with a specific charger are marked red.

 

It is worth noting that the cables with higher AWG size made from higher quality materials (non-doped, non-contaminated copper) and with better connectors will generate lower losses than those with higher thickness strands and doped e.g. with aluminium.

 

Electric cables that has been used in Europe for many years are manufactured to the metric standard BS 6722:1986. 1.5 mm2 and 2.5 mm2 diameter wires with permissible ampacity of 10 A and 16 A are most commonly used in the construction industry. In the countries using AWG system, No. 14 AWG (2.08 mm2) and No. 12 AWG (3.31 mm2) with maximum ampacity of 15 A and 20 A are concealed in the walls.

 


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