American wire gauge
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American wire gauge (AWG), also known as the "Brown and Sharpe" wire gauge, is used in the United States and other countries as a standard method of denoting wire diameter, especially for nonferrous, electrically conducting wire. The steel industry uses a different numbering system for their wire thickness gages (e.g. W&M Wire Gage or US Steel Wire Gage or the different Music Wire Gage) so data below does not apply to steel wire.
Increasing gauge numbers give decreasing wire diameters, which is similar to many other non-metric gauging systems. This seemingly-counterintuitive numbering is derived from the fact that the gauge number is related to the number of drawing operations that must be used to produce a given gauge of wire; very fine wire (for example, 30 gauge) requires far more passes through the drawing dies than does 0 gauge wire.
Note that for gauges 5 through about 14, the wire gauge is effectively the number of bare solid wires that, when placed side by side, span 1 inch. That is, 8 gauge is about 1/8" in diameter.
In the same fashion, AWG is also commonly used to specify body piercing jewelry sizes, especially larger sizes.[link]
Formulas
By definition, No. 36 AWG is 0.005 inches diameter, and No. 0000 is 0.46 inches diameter. The diameter increases by 0.46/0.005 = 92 times, evenly divided into 39 sizes. Therefore, the diameter of a No. n AWG wire is
- [d_n = 0.005~\mathrm \times 92 ^ \frac]
- [A_n = \frac d_n^2 = 0.000019635~\mathrm^2 \times 92 ^ \frac]
The ratio between successive sizes is the 39th root of 92, or approximately 1.1229322. [link]
The sixth power of this ratio is nearly 2.0, which means for an increase in 6 gauge numbers, the wire diameter is changed by a ratio of two (No. 10 is about one-half the diameter of No. 4 AWG). A decrease of three gauge numbers doubles the area of a wire. A decrease of 10 gauge numbers, for example from No. 10 to 1/0, multiplies the area and weight by approximately 10 and reduces the resistance by approximately 10.
Table of AWGs and approximate corresponding 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. The table below assumes DC or frequencies equal to or less than 60 Hz operation of the wires and does not take skin effect into account.
AWG Diameter Area Copper
resistanceCopper
resistanceCopper wire
current rating
with 60 °C insulationApproximate
stranded metric
equivalents(in) (mm) (mm²) (Ω/1 km) (Ω/1000 ft) (A) 000000(6/0) 0.5800 14.73 170 00000(5/0) 0.5165 13.12 135 0000(4/0) 0.4600 11.68 107 000(3/0) 0.4096 10.40 85 00(2/0) 0.3648 9.266 67.4 0(1/0) 0.3249 8.251 53.5 ~0.1 1 0.2893 7.348 42.4 110 2 0.2576 6.544 33.6 95 3 0.2294 5.827 26.7 85 196/0.4 4 0.2043 5.189 21.2 70 5 0.1819 4.621 16.8 126/0.4 6 0.1620 4.115 13.3 55 7 0.1443 3.665 10.5 80/0.4 8 0.1285 3.264 8.37 40 9 0.1144 2.906 6.63 >84/0.3 10 0.1019 2.588 5.26 0.9989 30 <84/0.3 11 0.0907 2.305 4.17 1.260 56/0.3 12 0.0808 2.053 3.31 1.588 20 13 0.0720 1.828 2.62 2.003 50/0.25 14 0.0641 1.628 2.08 2.525 15 15 0.0571 1.450 1.65 10.45 3.184 >30/0.25 16 0.0508 1.291 1.31 13.18 4.016 10 <30/0.25 17 0.0453 1.150 1.04 5.064 32/0.2 18 0.0403 1.024 0.823 6.385 >24/0.2 19 0.0359 0.9116 0.653 8.051 <24/0.2 20 0.0320 0.8118 0.518 10.15 16/0.2 21 0.0285 0.7229 0.410 12.80 22 0.0253 0.6438 0.326 16.14 7/0.25 23 0.0226 0.5733 0.258 20.36 24 0.0201 0.5106 0.205 25.67 1/0.5, 7/0.2, 30/0.1 25 0.0179 0.4547 0.162 32.37 26 0.0159 0.4049 0.129 40.81 7/0.15 27 0.0142 0.3606 0.102 51.47 28 0.0126 0.3211 0.081 64.90 29 0.0113 0.2859 0.0642 268.5 81.83 30 0.0100 0.2546 0.0509 103.2 1/0.25, 7/0.1 31 0.0089 0.2268 0.0404 130.1 32 0.0080 0.2019 0.0320 164.1 1/0.2, 7/0.08 33 0.0071 0.1798 0.0254 206.9 34 0.0063 0.1601 0.0201 260.9 35 0.0056 0.1426 0.0160 331.0 36 0.0050 0.1270 0.0127 414.8 37 0.0045 0.1131 0.0100 512.1 38 0.0040 0.1007 0.00797 648.6 39 0.0035 0.08969 0.00632 847.8 40 0.0031 0.07987 0.00501 1080.0 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 mm², 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 mm². 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 in 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 millimetre, millilitre etc.
Outside North America, wire sizes for electrical purposes are usually given as the cross sectional area in square millimetres. International standard manufacturing sizes for conductors in electrical cables are defined in IEC 60228.
Reference
- Donald G. Fink and H. Wayne Beaty, Standard Handbook for Electrical Engineers, Eleventh Edition,McGraw-Hill, New York, 1978, ISBN 007020974X, page 4-18 and table 4-11.
See also
- IEC 60228 for international standard wire sizes
- Imperial Wire Gauge & British Standard Gauge
- [Wikimedia chart] comparing all known wire gauges to each other.
External links
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