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Wire Gauge and Current Limits Including Skin Depth and Strength

December 17, 2014
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AWG Wire Sizes (see table below)

AWG: In the American Wire Gauge (AWG), diameters can be calculated by applying the formula D(AWG)=.005·92((36-AWG)/39) inch. For the 00, 000, 0000 etc. gauges you use -1, -2, -3, which makes more sense mathematically than "double nought." This means that in American wire gage every 6 gauge decrease gives a doubling of the wire diameter, and every 3 gauge decrease doubles the wire cross sectional area. Similar to dB in signal and power levels. An approximate but accurate enough form of this formula contributed by Mario Rodriguez is D = .460 * (57/64)(awg +3) or D = .460 * (0.890625)(awg +3).

Metric Wire Gauges (see table below)

Metric Gauge: In the Metric Gauge scale, the gauge is 10 times the diameter in millimeters, so a 50 gauge metric wire would be 5 mm in diameter. Note that in AWG the diameter goes up as the gauge goes down, but for metric gauges it is the opposite. Probably because of this confusion, most of the time metric sized wire is specified in millimeters rather than metric gauges.

Load Carrying Capacities (see table below)

The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. NOTE: For installations that need to conform to the National Electrical Code, you must use their guidelines. Contact your local electrician to find out what is legal!

Maximum Frequency for 100% Skin Depth

This data is useful for high frequency AC engineering. When high frequency AC is conducted by a wire there is a tendency for the current to flow along the outside of the wire. This increases the effective resistance. The frequency listed in the table shows the frequency at which the calculated skin depth is equal to the radius of the wire, and is an indication that above this frequency you should start considering the skin effect when calculating the wire's resistance.

Breaking Force for Cu Wire

This estimate is based on nick-free soft annealed wire having a tensile strength of 37000 pounds per square inch.

AWG gauge Conductor
Diameter Inches
Conductor
Diameter mm
Ohms per 1000 ft. Ohms per km Maximum amps for chassis wiring Maximum amps for
power transmission
Maximum frequency for
100% skin depth for solid conductor copper
Breaking force Soft Annealed Cu 37000 PSI
OOOO 0.46 11.684 0.049 0.16072 380 302 125 Hz 6120 lbs
OOO 0.4096 10.40384 0.0618 0.202704 328 239 160 Hz 4860 lbs
OO 0.3648 9.26592 0.0779 0.255512 283 190 200 Hz 3860 lbs
0 0.3249 8.25246 0.0983 0.322424 245 150 250 Hz 3060 lbs
1 0.2893 7.34822 0.1239 0.406392 211 119 325 Hz 2430 lbs
2 0.2576 6.54304 0.1563 0.512664 181 94 410 Hz 1930 lbs
3 0.2294 5.82676 0.197 0.64616 158 75 500 Hz 1530 lbs
4 0.2043 5.18922 0.2485 0.81508 135 60 650 Hz 1210 lbs
5 0.1819 4.62026 0.3133 1.027624 118 47 810 Hz 960 lbs
6 0.162 4.1148 0.3951 1.295928 101 37 1100 Hz 760 lbs
7 0.1443 3.66522 0.4982 1.634096 89 30 1300 Hz 605 lbs
8 0.1285 3.2639 0.6282 2.060496 73 24 1650 Hz 480 lbs
9 0.1144 2.90576 0.7921 2.598088 64 19 2050 Hz 380 lbs
10 0.1019 2.58826 0.9989 3.276392 55 15 2600 Hz 314 lbs
11 0.0907 2.30378 1.26 4.1328 47 12 3200 Hz 249 lbs
12 0.0808 2.05232 1.588 5.20864 41 9.3 4150 Hz 197 lbs
13 0.072 1.8288 2.003 6.56984 35 7.4 5300 Hz 150 lbs
14 0.0641 1.62814 2.525 8.282 32 5.9 6700 Hz 119 lbs
15 0.0571 1.45034 3.184 10.44352 28 4.7 8250 Hz 94 lbs
16 0.0508 1.29032 4.016 13.17248 22 3.7 11 k Hz 75 lbs
17 0.0453 1.15062 5.064 16.60992 19 2.9 13 k Hz 59 lbs
18 0.0403 1.02362 6.385 20.9428 16 2.3 17 kHz 47 lbs
19 0.0359 0.91186 8.051 26.40728 14 1.8 21 kHz 37 lbs
20 0.032 0.8128 10.15 33.292 11 1.5 27 kHz 29 lbs
21 0.0285 0.7239 12.8 41.984 9 1.2 33 kHz 23 lbs
22 0.0254 0.64516 16.14 52.9392 7 0.92 42 kHz 18 lbs
23 0.0226 0.57404 20.36 66.7808 4.7 0.729 53 kHz 14.5 lbs
24 0.0201 0.51054 25.67 84.1976 3.5 0.577 68 kHz 11.5 lbs
25 0.0179 0.45466 32.37 106.1736 2.7 0.457 85 kHz 9 lbs
26 0.0159 0.40386 40.81 133.8568 2.2 0.361 107 kH 7.2 lbs
27 0.0142 0.36068 51.47 168.8216 1.7 0.288 130 kHz 5.5 lbs
28 0.0126 0.32004 64.9 212.872 1.4 0.226 170 kHz 4.5 lbs
29 0.0113 0.28702 81.83 268.4024 1.2 0.182 210 kHz 3.6 lbs
30 0.01 0.254 103.2 338.496 0.86 0.142 270 kHz 2.75 lbs
31 0.0089 0.22606 130.1 426.728 0.7 0.113 340 kHz 2.25 lbs
32 0.008 0.2032 164.1 538.248 0.53 0.091 430 kHz 1.8 lbs
Metric 2.0 0.00787 0.200 169.39 555.61 0.51 0.088 440 kHz  
33 0.0071 0.18034 206.9 678.632 0.43 0.072 540 kHz 1.3 lbs
Metric 1.8 0.00709 0.180 207.5 680.55 0.43 0.072 540 kHz  
34 0.0063 0.16002 260.9 855.752 0.33 0.056 690 kHz 1.1 lbs
Metric 1.6 0.0063 0.16002 260.9 855.752 0.33 0.056 690 kHz  
35 0.0056 0.14224 329 1079.12 0.27 0.044 870 kHz 0.92 lbs
Metric 1.4 .00551 .140 339 1114 0.26 0.043 900 kHz  
36 0.005 0.127 414.8 1360 0.21 0.035 1100 kHz 0.72 lbs
Metric 1.25 .00492 0.125 428.2 1404 0.20 0.034 1150 kHz  
37 0.0045 0.1143 523.1 1715 0.17 0.0289 1350 kHz 0.57 lbs
Metric 1.12 .00441 0.112 533.8 1750 0.163 0.0277 1400 kHz  
38 0.004 0.1016 659.6 2163 0.13 0.0228 1750 kHz 0.45 lbs
Metric 1 .00394 0.1000 670.2 2198 0.126 0.0225 1750 kHz  
39 0.0035 0.0889 831.8 2728 0.11 0.0175 2250 kHz 0.36 lbs
40 0.0031 0.07874 1049 3440 0.09 0.0137 2900 kHz 0.29 lbs
               
Voltage Drop Calculator by Gerald Newton http://www.electrician2.com

The following calculator calculates the voltage drop, and voltage at the end of the wire for American Wire Gauge from 4/0 AWG to 30 AWG, aluminum or copper wire. (Note: It just calculates the voltage drop, consult the above table for rules-of-thumb, or your local or national electrical code or your electrician to decide what is legal!) Note that the voltage drop does not depend on the input voltage, just on the resistance of the wire and the load in amps.

Select Copper or Aluminum

Select American Wire Gauge (AWG) Size

Select Voltage

Enter 1-way circuit
length in feet (the calculation is for the round trip distance)

Enter Load
in amps


Voltage drop

Voltage at load end of circuit

Per Cent voltage drop

Wire cross section in circular mils

 

This chart of American Wire Gauge (AWG) wire sizes and rated ampacities is data intended for the pleasure of our readers only. Typographical errors, etc. are probable, since the typist is not a professional (our CEO). Please point out errors. The data listed are incomplete and should be used as a guideline only. Please contact manufacturers for the latest data.

We hope that this information is helpful. Now go out and design something that needs a charger, power supply, or battery pack!


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