American wire gauge

American wire gauge

American wire gauge (AWG), also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used since 1857 predominantly in the United States for the diameters of round, solid, nonferrous, electrically conducting wire. [ASTM Standard B 258-02, "Standard specification for standard nominal diameters and cross-sectional areas of AWG sizes of solid round wires used as electrical conductors", ASTM International, 2002 ] The cross-sectional area of each gauge is an important factor for determining its current-carrying capacity.

The steel industry uses different wire gauges (for example, W&M Wire Gauge or US Steel Wire Gauge, or Music Wire Gauge). The table 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 gauge system originated in the the number of drawing operations used to produce a given gauge of wire. Very fine wire (for example, 30 gauge) requires more passes through the drawing dies than does 0 gauge wire. Manufacturers of wire formerly had proprietary wire gauge systems; the development of standardized wire gauges rationalized selection of wire for a particular purpose.

The AWG tables are for a single, solid, round conductor. When a stranded wire needs to be converted to an AWG equivalent size, the total cross-sectional area of the conductor, which determines its current-carrying capacity and electrical resistance (not its diameter), is taken as the determining factor. This permits stranded wire to have a slightly different overall diameter than solid wire having the same AWG.

The AWG size is one of the essential specifications that are printed on data cables. For instance, an AWG of 24 is common for network cables such as a Category 5 UTP, and an AWG of 26 is the norm for Serial ATA cables.

AWG is also commonly used to specify body piercing jewelry sizes, especially smaller sizes. [ [http://www.steelnavel.com/reference.asp Body Piercing Jewelry Size Reference - SteelNavel.com] ]

Formula

By definition, No. 36 AWG is 0.005 inches in diameter, and No. 0000 is 0.46 inches in diameter. The ratio of these diameters is 92, and there are 40 gauge sizes from No. 36 to No. 0000, or 39 steps. Using this common ratio, wire gauge sizes vary geometrically according to the following formula: The diameter of a No. "n" AWG wire is

:d_n = 0.005~mathrm{inch} imes 92 ^ frac{36-n}{39}

or

:d_n = 0.005~mathrm{mm} imes 25.4 imes 92 ^ frac{36-n}{39}

the gauge can be calculated from the diameter using

:n=-39log_{92} left( frac{d_{n{0.005~mathrm{inch ight)+36 [The logarithm to the base 92 can be computed using any other logarithm, such as common or natural logarithm, using log92"x" = (log "x")/(log 92).]

and the cross-section area is:A_n = frac{pi}{4} d_n^2 = 0.000019635~mathrm{inch}^2 imes 92 ^ frac{36-n}{19.5}.

Sizes with multiple zeros are successively larger than No. 0 and can be denoted using "number of zeros"/0", for example 4/0 for 0000. For an "m"/0 AWG wire, use "n" = −("m"−1) in the above formulas. For instance, for No. 0000 or 4/0, use n = −3.

The ASTM B 258-02 standard defines the ratio between successive sizes to be the 39th root of 92, or approximately 1.1229322. [ASTM Standard B 258-02, page 4] ASTM B 258-02 also dictates that wire diameters should be tabulated with no more than 4 significant figures, with a resolution of no more than 0.0001 inches (0.1 mils) for wires larger than No. 44 AWG, and 0.00001 inches (0.01 mils) for wires No. 45 AWG and smaller.

Rules of Thumb

The sixth power of this ratio is very close to 2 [The result is roughly 2.0050, or one-quarter of one percent higher than 2] , which leads to the following rules of thumb:
*When the "diameter" of a wire is doubled, the AWG will decrease by 6. (e.g. No. 2 AWG is about twice the diameter of No. 8 AWG.)
*When the "area" of a wire is doubled, the AWG will decrease by 3. (e.g. Two No. 14 AWG wires have about the same cross-sectional area as a single No. 11 AWG wire.)

Additionally, a decrease of ten 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 AWG wire 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 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 with no insulation.

:

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. Some common cables are midway between two AWG sizes. 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 cylinder with 1000 mil = 1 inch diameter. An older abbreviation for one thousand circular mils is "MCM".

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.

Note that the area in mm² may differ somewhat from the numbers given in the table, depending on number of strands etc.

Pronunciation

"AWG" is colloquially referred to as "gauge" and the zeros in large wire sizes are referred to as "aught" (PronEng|ɔːt). Wire sized 1 AWG is referred to as "one gauge"; similarly, smaller diameters are pronounced "x" gauge", where "x" is the positive integer AWG number. Larger wire (#0 and up) is referred to as "one aught", "two aught" etc, depending on how many zeros are in the AWG rating. [ [http://www.event-solutions.com/web_extras/february_2006/glossary_of_power_terms Glossary of Power Terms | Event Solutions ] ]

References

*Donald G. Fink and H. Wayne Beaty, "Standard Handbook for Electrical Engineers, Eleventh Edition",McGraw-Hill, New York, 1978, ISBN 0-07-020974-X, page 4-18 and table 4-11.

ee also

*IEC 60228 for international standard wire sizes
*Imperial Wire Gauge & British Standard Gauge
*

External links

* [http://www.66pacific.com/calculators/wire_calc.aspx Wire Gauge to Diameter—Diameter to Wire Gauge Converter] - Online calculator converts gauge to diameter or diameter to gauge for any wire size.
* [http://www.ultracad.com/articles/wiregauge.pdf How to Gauge Traces]
* [http://www.sengpielaudio.com/calculator-cross-section.htm Conversion and calculation of cable diameter to AWG and vice versa]
* [http://www.bnoack.com/index.html?http&&&www.bnoack.com/data/wire-resistance.html Table of wire resistivities for bigger gauge (insulation included)]
* [http://www.litz-wire.com/wirediminsions.html Bare copper wire AWG NEMA/IEC metric standard sizes ]
* [http://www.powerstream.com/Wire_Size.htm Reference for conversions and maximum safe current loads]


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