American Wire Gauge (AWG) is a logarithmic stepped standardized wire gauge system used since 1857, predominantly in North America, for the diameters of round, solid, nonferrous, electrically conducting wire. Dimensions of the wires are given in ASTM standard B 258. [1] The cross-sectional area of each gauge is an important factor for determining its current-carrying capacity.
AWG is also commonly used to specify body piercing jewelry sizes (especially smaller sizes), even when the material is not metallic. [2]
The AWG originated in the number of drawing operations used to produce a given gauge of wire. Very fine wire (for example, 30 gauge) required more passes through the drawing dies than 0 gauge wire did. Manufacturers of wire formerly had proprietary wire gauge systems; the development of standardized wire gauges rationalized selection of wire for a particular purpose.
While the AWG is essentially identical to the Brown & Sharpe (B&S) sheet metal gauge, the B&S gauge was designed for use with sheet metals as its name suggests. These are functionally interchangeable but the use of B&S in relation to wire gauges, rather than sheet metal gauges, is technically improper.
Increasing gauge numbers denote logarithmically decreasing wire diameters, which is similar to many other non-metric gauging systems such as British Standard Wire Gauge (SWG). However, AWG is dissimilar to IEC 60228, the metric wire-size standard used in most parts of the world, based directly on the wire cross-section area (in square millimetres, mm²).
The AWG tables are for a single, solid and round conductor. The AWG of a stranded wire is determined by the cross-sectional area of the equivalent solid conductor. Because there are also small gaps between the strands, a stranded wire will always have a slightly larger overall diameter than a solid wire with the same AWG.
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 1:92, and there are 40 gauge sizes from No. 36 to No. 0000, or 39 steps. Because each successive gauge number increases cross sectional area by a constant multiple, diameters vary geometrically. Any two successive gauges (e.g., A and B ) have diameters whose ratio (dia. B ÷ dia. A) is (approximately 1.12293), while for gauges two steps apart (e.g., A, B, and C), the ratio of the C to A is about 1.122932 ≈ 1.26098.
The diameter of an AWG wire is determined according to the following formula:
(where n is the AWG size for gauges from 36 to 0, n = −1 for No. 00, n = −2 for No. 000, and n = −3 for No. 0000. See below for rule)
or equivalently:
The gauge can be calculated from the diameter using [3]
and the cross-section area is
The standard ASTM B258-02 (2008), Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors, defines the ratio between successive sizes to be the 39th root of 92, or approximately 1.1229322. [4] ASTM B258-02 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.
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) = 1 − m in the above formulas. For instance, for No. 0000 or 4/0, use n = −3.
The sixth power of 39√92 is very close to 2, [5] which leads to the following rules of thumb:
The table below shows various data including both the resistance of the various wire gauges and the allowable current (ampacity) based on a copper conductor with plastic insulation. The diameter information in the table applies to solid wires. Stranded wires are calculated by calculating the equivalent cross sectional copper area. Fusing current (melting wire) is estimated based on 25 °C (77 °F) ambient temperature. 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 per unit length" is the reciprocal of the conductor diameter; it is therefore an upper limit for wire wound in the form of a helix (see solenoid), based on uninsulated wire.
AWG | Diameter | Turns of wire, without insulation | Area | Copper wire | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Length-specific resistance [7] | Ampacity at temperature rating [lower-alpha 1] | Fusing current [10] [11] | ||||||||||||
60 °C | 75 °C | 90 °C | Preece [12] [13] [14] [15] | Onderdonk [16] [15] | ||||||||||
(in) | (mm) | (per in) | (per cm) | (kcmil) | (mm2) | (mΩ/m [lower-alpha 2] ) | (mΩ/ft [lower-alpha 3] ) | (A) | ~10 s | 1 s | 32 ms | |||
0000 (4/0) | 0.4600 [lower-alpha 4] | 11.684 [lower-alpha 4] | 2.17 | 0.856 | 212 | 107 | 0.1608 | 0.04901 | 195 | 230 | 260 | 3.2 kA | 33 kA | 182 kA |
000 (3/0) | 0.4096 | 10.405 | 2.44 | 0.961 | 168 | 85.0 | 0.2028 | 0.06180 | 165 | 200 | 225 | 2.7 kA | 26 kA | 144 kA |
00 (2/0) | 0.3648 | 9.266 | 2.74 | 1.08 | 133 | 67.4 | 0.2557 | 0.07793 | 145 | 175 | 195 | 2.3 kA | 21 kA | 115 kA |
0 (1/0) | 0.3249 | 8.251 | 3.08 | 1.21 | 106 | 53.5 | 0.3224 | 0.09827 | 125 | 150 | 170 | 1.9 kA | 16 kA | 91 kA |
1 | 0.2893 | 7.348 | 3.46 | 1.36 | 83.7 | 42.4 | 0.4066 | 0.1239 | 110 | 130 | 145 | 1.6 kA | 13 kA | 72 kA |
2 | 0.2576 | 6.544 | 3.88 | 1.53 | 66.4 | 33.6 | 0.5127 | 0.1563 | 95 | 115 | 130 | 1.3 kA | 10.2 kA | 57 kA |
3 | 0.2294 | 5.827 | 4.36 | 1.72 | 52.6 | 26.7 | 0.6465 | 0.1970 | 85 | 100 | 115 | 1.1 kA | 8.1 kA | 45 kA |
4 | 0.2043 | 5.189 | 4.89 | 1.93 | 41.7 | 21.2 | 0.8152 | 0.2485 | 70 | 85 | 95 | 946 A | 6.4 kA | 36 kA |
5 | 0.1819 | 4.621 | 5.50 | 2.16 | 33.1 | 16.8 | 1.028 | 0.3133 | 795 A | 5.1 kA | 28 kA | |||
6 | 0.1620 | 4.115 | 6.17 | 2.43 | 26.3 | 13.3 | 1.296 | 0.3951 | 55 | 65 | 75 | 668 A | 4.0 kA | 23 kA |
7 | 0.1443 | 3.665 | 6.93 | 2.73 | 20.8 | 10.5 | 1.634 | 0.4982 | 561 A | 3.2 kA | 18 kA | |||
8 | 0.1285 | 3.264 | 7.78 | 3.06 | 16.5 | 8.37 | 2.061 | 0.6282 | 40 | 50 | 55 | 472 A | 2.5 kA | 14 kA |
9 | 0.1144 | 2.906 | 8.74 | 3.44 | 13.1 | 6.63 | 2.599 | 0.7921 | 396 A | 2.0 kA | 11 kA | |||
10 | 0.1019 | 2.588 | 9.81 | 3.86 | 10.4 | 5.26 | 3.277 | 0.9989 | 30 | 35 | 40 | 333 A | 1.6 kA | 8.9 kA |
11 | 0.0907 | 2.305 | 11.0 | 4.34 | 8.23 | 4.17 | 4.132 | 1.260 | 280 A | 1.3 kA | 7.1 kA | |||
12 | 0.0808 | 2.053 | 12.4 | 4.87 | 6.53 | 3.31 | 5.211 | 1.588 | 20 | 25 | 30 | 235 A | 1.0 kA | 5.6 kA |
13 | 0.0720 | 1.828 | 13.9 | 5.47 | 5.18 | 2.62 | 6.571 | 2.003 | 198 A | 798 A | 4.5 kA | |||
14 | 0.0641 | 1.628 | 15.6 | 6.14 | 4.11 | 2.08 | 8.286 | 2.525 | 15 | 20 | 25 | 166 A | 633 A | 3.5 kA |
15 | 0.0571 | 1.450 | 17.5 | 6.90 | 3.26 | 1.65 | 10.45 | 3.184 | 140 A | 502 A | 2.8 kA | |||
16 | 0.0508 | 1.291 | 19.7 | 7.75 | 2.58 | 1.31 | 13.17 | 4.016 | 18 | 117 A | 398 A | 2.2 kA | ||
17 | 0.0453 | 1.150 | 22.1 | 8.70 | 2.05 | 1.04 | 16.61 | 5.064 | 99 A | 316 A | 1.8 kA | |||
18 | 0.0403 | 1.024 | 24.8 | 9.77 | 1.62 | 0.823 | 20.95 | 6.385 | 10 | 14 | 16 | 83 A | 250 A | 1.4 kA |
19 | 0.0359 | 0.912 | 27.9 | 11.0 | 1.29 | 0.653 | 26.42 | 8.051 | — | — | — | 70 A | 198 A | 1.1 kA |
20 | 0.0320 | 0.812 | 31.3 | 12.3 | 1.02 | 0.518 | 33.31 | 10.15 | 5 | 11 | — | 58.5 A | 158 A | 882 A |
21 | 0.0285 | 0.723 | 35.1 | 13.8 | 0.810 | 0.410 | 42.00 | 12.80 | — | — | — | 49 A | 125 A | 700 A |
22 | 0.0253 | 0.644 | 39.5 | 15.5 | 0.642 | 0.326 | 52.96 | 16.14 | 3 | 7 | — | 41 A | 99 A | 551 A |
23 | 0.0226 | 0.573 | 44.3 | 17.4 | 0.509 | 0.258 | 66.79 | 20.36 | — | — | — | 35 A | 79 A | 440 A |
24 | 0.0201 | 0.511 | 49.7 | 19.6 | 0.404 | 0.205 | 84.22 | 25.67 | 2.1 | 3.5 | — | 29 A | 62 A | 348 A |
25 | 0.0179 | 0.455 | 55.9 | 22.0 | 0.320 | 0.162 | 106.2 | 32.37 | — | — | — | 24 A | 49 A | 276 A |
26 | 0.0159 | 0.405 | 62.7 | 24.7 | 0.254 | 0.129 | 133.9 | 40.81 | 1.3 | 2.2 | — | 20 A | 39 A | 218 A |
27 | 0.0142 | 0.361 | 70.4 | 27.7 | 0.202 | 0.102 | 168.9 | 51.47 | — | — | — | 17 A | 31 A | 174 A |
28 | 0.0126 | 0.321 | 79.1 | 31.1 | 0.160 | 0.0810 | 212.9 | 64.90 | 0.83 | 1.4 | — | 14 A | 24 A | 137 A |
29 | 0.0113 | 0.286 | 88.8 | 35.0 | 0.127 | 0.0642 | 268.5 | 81.84 | — | — | — | 12 A | 20 A | 110 A |
30 | 0.0100 | 0.255 | 99.7 | 39.3 | 0.101 | 0.0509 | 338.6 | 103.2 | 0.52 | 0.86 | — | 10 A | 15 A | 86 A |
31 | 0.00893 | 0.227 | 112 | 44.1 | 0.0797 | 0.0404 | 426.9 | 130.1 | — | — | — | 9 A | 12 A | 69 A |
32 | 0.00795 | 0.202 | 126 | 49.5 | 0.0632 | 0.0320 | 538.3 | 164.1 | 0.32 | 0.53 | — | 7 A | 10 A | 54 A |
33 | 0.00708 | 0.180 | 141 | 55.6 | 0.0501 | 0.0254 | 678.8 | 206.9 | — | — | — | 6 A | 7.7 A | 43 A |
34 | 0.00630 | 0.160 | 159 | 62.4 | 0.0398 | 0.0201 | 856.0 | 260.9 | 0.18 | 0.3 | — | 5 A | 6.1 A | 34 A |
35 | 0.00561 | 0.143 | 178 | 70.1 | 0.0315 | 0.0160 | 1079 | 329.0 | — | — | — | 4 A | 4.8 A | 27 A |
36 | 0.00500 [lower-alpha 4] | 0.127 [lower-alpha 4] | 200 | 78.7 | 0.0250 | 0.0127 | 1361 | 414.8 | — | — | — | 4 A | 3.9 A | 22 A |
37 | 0.00445 | 0.113 | 225 | 88.4 | 0.0198 | 0.0100 | 1716 | 523.1 | — | — | — | 3 A | 3.1 A | 17 A |
38 | 0.00397 | 0.101 | 252 | 99.3 | 0.0157 | 0.00797 | 2164 | 659.6 | — | — | — | 3 A | 2.4 A | 14 A |
39 | 0.00353 | 0.0897 | 283 | 111 | 0.0125 | 0.00632 | 2729 | 831.8 | — | — | — | 2 A | 1.9 A | 11 A |
40 | 0.00314 | 0.0799 | 318 | 125 | 0.00989 | 0.00501 | 3441 | 1049 | — | — | — | 1 A | 1.5 A | 8.5 A |
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. The next wire size larger than 4/0 has a cross section of 250 kcmil. A circular mil is the area of a wire one mil in diameter. One million circular mils is the area of a circle with 1,000 mil (1 inch) diameter. An older abbreviation for one thousand circular mils is MCM.
AWG can also be used to describe stranded wire. The AWG of a stranded wire represents the sum of the cross-sectional diameter of the individual strands; the gaps between strands are not counted. When made with circular strands, these gaps occupy about 25% of the wire area, thus requiring the overall bundle diameter to be about 13% larger than a solid wire of equal gauge.
Stranded wires are specified with three numbers, the overall AWG size, the number of strands, and the AWG size of a strand. The number of strands and the AWG of a strand are separated by a slash. For example, a 22 AWG 7/30 stranded wire is a 22 AWG wire made from seven strands of 30 AWG wire.
As indicated in the Formulas and Rules of Thumb sections above, differences in AWG translate directly into ratios of diameter or area. This property can be employed to easily find the AWG of a stranded bundle by measuring the diameter and count of its strands. (This only applies to bundles with circular strands of identical size.) To find the AWG of 7-strand wire with equal strands, subtract 8.4 from the AWG of a strand. Similarly, for 19-strand subtract 12.7, and for 37 subtract 15.6.
Measuring strand diameter is often easier and more accurate than attempting to measure bundle diameter and packing ratio. Such measurement can be done with a wire gauge go-no-go tool or with a caliper or micrometer.
Alternative ways are commonly used in the electrical industry to specify wire sizes as AWG.
AWG is colloquially referred to as gauge and the zeros in large wire sizes are referred to as aught /ˈɔːt/ . Wire sized 1 AWG is referred to as "one gauge" or "No. 1" wire; similarly, smaller diameters are pronounced "x gauge" or "No. x" wire, where x is the positive-integer AWG number. Consecutive AWG wire sizes larger than No. 1 wire are designated by the number of zeros:
and so on.
A wire is a flexible, round, bar of metal.
Twisted pair cabling is a type of communications cable in which two conductors of a single circuit are twisted together for the purposes of improving electromagnetic compatibility. Compared to a single conductor or an untwisted balanced pair, a twisted pair reduces electromagnetic radiation from the pair and crosstalk between neighbouring pairs and improves rejection of external electromagnetic interference. It was invented by Alexander Graham Bell.
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge in one or more directions. Materials made of metal are common electrical conductors. The flow of negatively charged electrons generates electric current, positively charged holes, and positive or negative ions in some cases.
In electromagnetism, skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases exponentially with greater depths in the conductor. It is caused by opposing eddy currents induced by the changing magnetic field resulting from the alternating current. The electric current flows mainly at the skin of the conductor, between the outer surface and a level called the skin depth. Skin depth depends on the frequency of the alternating current; as frequency increases, current flow becomes more concentrated near the surface, resulting in less skin depth. Skin effect reduces the effective cross-section of the conductor and thus increases its effective resistance. At 60 Hz in copper, skin depth is about 8.5 mm. At high frequencies, skin depth becomes much smaller.
Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure.
A power cable is an electrical cable, an assembly of one or more electrical conductors, usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring within buildings, buried in the ground, run overhead, or exposed. Power cables that are bundled inside thermoplastic sheathing and that are intended to be run inside a building are known as NM-B.
IEC 60228 is the International Electrotechnical Commission (IEC)'s international standard on conductors of insulated cables. As of 2023 the current version is Third Edition 2004-11 Among other things, it defines a set of standard wire cross-sectional areas:
Litz wire is a particular type of multistrand wire or cable used in electronics to carry alternating current (AC) at radio frequencies. The wire is designed to reduce the skin effect and proximity effect losses in conductors used at frequencies up to about 1 MHz.
Aluminum building wiring is a type of electrical wiring for residential construction or houses that uses aluminum electrical conductors. Aluminum provides a better conductivity-to-weight ratio than copper, and therefore is also used for wiring power grids, including overhead power transmission lines and local power distribution lines, as well as for power wiring of some airplanes. Utility companies have used aluminum wire for electrical transmission in power grids since around the late 1800s to the early 1900s. It has cost and weight advantages over copper wires. Aluminum in power transmission and distribution applications is still the preferred wire material today.
Speaker wire is used to make the electrical connection between loudspeakers and audio amplifiers. Modern speaker wire consists of two or more electrical conductors individually insulated by plastic or, less commonly, rubber. The two wires are electrically identical, but are marked to identify the correct audio signal polarity. Most commonly, speaker wire comes in the form of zip cord.
Wire gauge is a measurement of wire diameter. This determines the amount of electric current the wire can safely carry, as well as its electrical resistance and weight.
A circular mil is a unit of area, equal to the area of a circle with a diameter of one mil. It corresponds to approximately 5.067×10−4 mm2. It is a unit intended for referring to the area of a wire with a circular cross section. As the definition of the unit contains π, it is easy to calculate area values in circular mils when the diameter in mils is known.
A thermoplastic-sheathed cable (TPS) consists of a toughened outer sheath of polyvinyl chloride (PVC) thermoplastic, covering one or more individual annealed copper conductors, themselves insulated with PVC. This type of wiring is commonly used for residential and light commercial construction in many countries. The flat version of the cable, with two insulated conductors and an uninsulated earth conductor, is referred to as twin and earth. In mainland Europe, a round equivalent is more common.
Magnet wire or enameled wire is a copper or aluminium wire coated with a very thin layer of insulation. It is used in the construction of transformers, inductors, motors, generators, speakers, hard disk head actuators, electromagnets, electric guitar pickups, and other applications that require tight coils of insulated wire.
Jewelry wire is wire, usually copper, brass, nickel, aluminium, silver, or gold, used in jewelry making.
Aluminium conductor steel-reinforced cable (ACSR) is a type of high-capacity, high-strength stranded conductor typically used in overhead power lines. The outer strands are high-purity aluminium, chosen for its good conductivity, low weight, low cost, resistance to corrosion and decent mechanical stress resistance. The centre strand is steel for additional strength to help support the weight of the conductor. Steel is of higher strength than aluminium which allows for increased mechanical tension to be applied on the conductor. Steel also has lower elastic and inelastic deformation due to mechanical loading as well as a lower coefficient of thermal expansion under current loading. These properties allow ACSR to sag significantly less than all-aluminium conductors. As per the International Electrotechnical Commission (IEC) and The CSA Group naming convention, ACSR is designated A1/S1A.
British Standard Wire Gauge is a unit for denoting wire size given by BS 3737:1964. It is also known as the Imperial Wire Gauge or British Standard Gauge. Use of SWG sizes has fallen greatly in popularity, but they are still used as a measure of thickness in guitar strings and some electrical wire. Cross sectional area in square millimetres is now the more usual size measurement for wires used in electrical installation cables. The current British Standard for metallic materials such as wire and sheet is BS 6722:1986, which is a solely metric standard.
Copper has been used in electrical wiring since the invention of the electromagnet and the telegraph in the 1820s. The invention of the telephone in 1876 created further demand for copper wire as an electrical conductor.
Body jewelry sizes express the thickness of an item of body jewelry, using one of several possible systems.
Telecommunications power cable, as described in Telcordia GR-347 & GR-347, consist of a stranded copper conductor used in AC/DC circuits up to 600 V that are insulated with non-halogen, limited smoke, polyolefin materials that are heat-resistant, moisture-resistant, and flame-retardant. These cables are provided as either Class B (standard) or Class I (flexible) products.