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American wire gauge
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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.

Origin

[edit]

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. These are functionally interchangeable, but the use of B&S in relation to wire gauges, rather than sheet metal gauges, is technically improper.

Specifications

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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.

Formulae

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By definition, 36 AWG is 0.005 inches in diameter, and 0000 AWG is 0.46 inches in diameter. The ratio of these diameters is 1:92, and there are 40 gauge sizes from 36 to 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. Similarly for gauges n steps apart the ratio of the first to last gauges is about 1.12293n.

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 00, n = −2 for 000, and n = −3 for 0000. See below for rule.)

or equivalently:

The gauge can be calculated from the diameter using [2]

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.[3] 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 thicker than 44 AWG, and 0.00001 inches (0.01 mils) for wires 45 AWG and thinner.

Sizes with multiple zeros are successively thicker than 0 AWG and can be denoted using "number of zeros/0", for example 4/0 AWG for 0000 AWG. For an m/0 AWG wire, use n = −(m − 1) = 1 − m in the above formulas. For instance, for 0000 AWG or 4/0 AWG, use n = −3.

Rules of thumb

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The sixth power of is very close to 2,[4] which leads to the following rules of thumb:

  • When the cross-sectional area of a wire is doubled, the AWG will decrease by 3; for example, two 14 AWG wires have about the same cross-sectional area as a single 11 AWG wire. This doubles the electrical conductance.
  • When the diameter of a solid round wire is doubled, the AWG will decrease by 6; for example, 1 mm diameter wire is ≈18 AWG, 2 mm diameter wire is ≈12 AWG, and 4 mm diameter wire is ≈6 AWG. This quadruples the cross-sectional area and conductance.
  • A decrease of ten gauge numbers; for example, from 24 AWG to 14 AWG multiplies the area, weight, and conductance by approximately 10.

Convenient coincidences result in the following rules of thumb for resistances:

  • The resistance of copper wire is approximately ⁠1 Ω/1000 ft⁠ for 10 AWG, ⁠10 Ω/1000 ft⁠ for 20 AWG, ⁠100 Ω/1000 ft⁠ for 30 AWG, and so on.[5]: 27  For an arbitrary gauge n, it is approximately 10n/10 Ω per 10000 ft.
  • Because aluminum wire has a conductivity of approximately 61% of copper, an aluminum wire has nearly the same resistance as a copper wire that is two sizes smaller, which has 62.9% of the area.

Tables of AWG wire sizes

[edit]

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 wire 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[6] 		Ampacity at temperature rating[a] Fusing current[9][10]
60 °C 75 °C 90 °C Preece[11][12][13][14] Onderdonk[15][14]
(in) (mm) (per in) (per cm) (kcmil) (mm2) (mΩ/m[b]) (mΩ/ft[c]) (A) ~10 s 1 s 32 ms
0000 (4/0) 0.4600[d] 11.684[d] 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 12 16 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[d] 0.127[d] 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
  1. ^ For enclosed wire at 30 °C ambient,[7] with given insulation material temperature rating, or for single unbundled wires in equipment for 16 AWG and thinner.[8]
  2. ^ or, equivalently, Ω/km
  3. ^ or, equivalently, Ω/kft
  4. ^ a b c d Exactly, by definition

In the North American electrical industry, conductors thicker 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 thicker 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.

Stranded wire AWG sizes

[edit]

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 Formulae 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.

Nomenclature and abbreviations in electrical distribution

[edit]
Main article: Electric power distribution

Alternative ways are commonly used in the electrical industry to specify wire sizes as AWG.

  • 4 AWG (proper)
    • #4 (the number sign is used as an abbreviation of "number")
    • № 4 (the numero sign is used as an abbreviation for "number")
    • No. 4 (an approximation of the numero is used as an abbreviation for "number")
    • No. 4 AWG
    • 4 ga. (abbreviation for "gauge")
  • 000 AWG (proper for thick sizes)
    • 3/0 (common for thick sizes) Pronounced "three-aught" or "triple-aught"
    • 3/0 AWG
    • #000

Pronunciation

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AWG is colloquially referred to as gauge and the zeros in thick wire sizes are referred to as aught /ˈɔːt/. Wire sized 1 AWG is referred to as "one gauge" or "No. 1" wire; similarly, thinner sizes are pronounced "x gauge" or "No. x" wire, where x is the positive-integer AWG number. Consecutive AWG wire sizes thicker than No. 1 wire are designated by the number of zeros:

  • No. 0, often written 1/0 and referred to as "one-aught" or "single-aught" wire
  • No. 00, often written 2/0 and referred to as "two-aught" or "double-aught" wire
  • No. 000, often written 3/0 and referred to as "three-aught" or "triple-aught" wire

and so on.

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

American wire gauge

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The American Wire Gauge (AWG), also known as the wire gauge, is a standardized logarithmic system used primarily in to specify the and cross-sectional area of solid, round, electrically conducting wire, especially for non-ferrous metals like and aluminum. It provides a consistent method for manufacturers, engineers, and electricians to select wire sizes based on current-carrying capacity, resistance, and mechanical properties, with gauge numbers ranging from 0000 (the thickest, with a nominal of 0.4600 inches or 11.684 mm) to 40 or smaller (the thinnest, with diameters as fine as 0.0031 inches or 0.079 mm). The system ensures interoperability in electrical applications, from household wiring to industrial cabling, by linking wire dimensions to performance metrics like and . AWG originated in 1857 when Joseph Rogers Brown, a founder of the Manufacturing Company, developed it to unify disparate wire sizing practices in the United States, replacing inconsistent local standards with a single, practical gauge based on wire-drawing dies. The gauge's non-linear progression means that each step in the numerical sequence reduces the wire's by a factor of approximately 1/1.1229 (about 10.9%), halving the cross-sectional area every three steps and thus doubling the electrical resistance per unit length, which facilitates calculations for . Initially adopted for non-ferrous wires, it was formalized through early 20th-century publications by the National Bureau of Standards (now NIST) and later refined in 1961 by the American Society for Testing and Materials (ASTM) to extend the range and adjust finer sizes for precision. Today, AWG remains the dominant wire sizing standard in the U.S. and , integrated into codes like the (), though it coexists with metric alternatives internationally. Key tables in standards such as NIST Handbook 100 and ASTM B258 detail nominal diameters, areas, resistances (e.g., 0.04901 ohms per 1000 feet for 0000 AWG at 20°C), and breaking strengths, enabling safe and efficient electrical installations across residential, commercial, and sectors. While primarily for solid conductors, AWG is also applied to stranded wires by equating total cross-sectional area to an equivalent solid gauge.

Definition and Standards

Core Definition

The American Wire Gauge (AWG) is a standardized for denoting the diameters of round, solid, non-ferrous electrically conducting wires, such as those made from and aluminum. In this , gauge numbers run inversely to wire : a higher AWG number corresponds to a smaller , while a lower number indicates a thicker wire. Predominantly used in , AWG standardizes conductor sizes to ensure consistency in electrical applications, facilitating interchangeability and compliance with safety codes. AWG follows a logarithmic, geometrical progression in wire diameters, enabling predictable scaling across sizes. Specifically, the of successive larger wires (decreasing gauge number) increases by a constant ratio of approximately 1.123, resulting in each step toward a higher gauge number decreasing the by about 10.9%. This progression squares to a factor of roughly 1.26 for cross-sectional area, meaning the area increases by about 26% for each decrease in gauge number (or decreases by approximately 21% per increase). The system spans from AWG 0000 (largest, 0.460 inches ) to AWG 40 and smaller (common fine sizes). The defining ratio is 92:1 over 39 steps from AWG 0000 to AWG 36, with the progression extending beyond this range using the same constant ratio of approximately 1.123 per step. AWG sizes directly influence key electrical properties, including resistance and current-carrying capacity (). Resistance per unit length varies inversely with cross-sectional area, so smaller-diameter (higher AWG) wires exhibit higher resistance, leading to greater power loss for a given current. , determined by factors like heat dissipation and material, generally increases with larger diameters (lower AWG numbers), allowing thicker wires to safely carry more current without overheating. These relations ensure AWG supports reliable design in wiring for power distribution, , and .

Standardization Bodies and History

The American Wire Gauge (AWG) system is primarily defined and maintained by , formerly the American Society for Testing and Materials, through its Standard Specification B258, which establishes the nominal diameters and cross-sectional areas for solid round wires across AWG sizes used in electrical conductors. This standard ensures consistency in wire dimensions for manufacturing and application in North American electrical systems. Originally approved in 1951 as B258-51T, it underwent significant revisions, including the extension of the gauge range and rounding of diameters, with the 1961 edition (B258-61) marking a key formalization that aligned with broader American standards. The (NEMA) supports AWG standardization by incorporating it into its specifications for wire and cable products, such as in NEMA MW 1000, which applies AWG sizing alongside metric equivalents to facilitate production and interoperability. Similarly, Underwriters Laboratories (UL) ensures compliance through rigorous testing and certification of wires meeting AWG dimensions, as outlined in its wire and cable guidelines, verifying safety and performance for listed products. Formal adoption of AWG as a standardized system occurred in the early 20th century, with the (AIEE) publishing the first comprehensive wire tables in via NBS Circular 31, establishing it as the basis for wire sizing . Integration into electrical codes advanced in the 1920s, including updates to the (NEC) that referenced AWG for conductor sizing to enhance safety in installations, with the second edition of the wire tables prefaced in 1925 reflecting these refinements. As of 2025, AWG standards have seen no major revisions since the , with the latest ASTM B258 update in 2018 maintaining the core specifications without substantive changes to dimensions or ranges. For global trade, AWG aligns with (IEC) metrics through established equivalence tables converting AWG sizes to square millimeters, enabling compatibility in international supply chains while preserving its primary use in .

Historical Development

Origins in the 19th Century

The wire gauge, which served as the foundation for the modern American Wire Gauge (AWG) system, was developed in 1857 by Joseph R. Brown, co-founder of the Manufacturing Company in . This innovation emerged during a period of rapid expansion in American manufacturing, particularly in the production of precision tools and equipment, where had established itself as a leader since its founding in 1833. The gauge was initially known as the Standard and was designed to provide a uniform method for measuring wire diameters, addressing the fragmented practices among wire producers at the time. The primary motivation for creating this gauge stemmed from the inconsistencies in wire sizing across manufacturers, which posed significant challenges for emerging industries such as . In the mid-19th century, the rapid growth of telegraph networks demanded reliable wire for long-distance transmission, but varying gauges led to mismatches in equipment compatibility and performance issues in electrical conductivity. Prior systems, like the Birmingham Wire Gauge, were inadequate for the precise needs of non-ferrous metals like , resulting in haphazard specifications that complicated and installation for telegraph companies. Brown's gauge aimed to rectify these problems by introducing a standardized scale tailored to wire, facilitating more efficient production and deployment in telegraph lines that were proliferating across the following Samuel Morse's demonstrations in the 1840s. At its core, the system employed a logarithmic progression based on successive wire-drawing operations, where each step reduces the by a factor of approximately 92^{-1/39}, covering sizes from 0000 AWG (the coarsest) to 36 AWG (the finest in the original system). This structure mirrored the practical realities of wire manufacturing, where each draw through a die progressively reduced the wire's in a geometric sequence, allowing for predictable scaling in cross-sectional area. The design prioritized non- metals, reflecting the company's expertise in working with materials like and , but it lacked broader applicability to wires and was not yet backed by any national regulatory framework. These early constraints highlighted the gauge's origins as a practical tool for industrial rather than a comprehensive universal measure.

Evolution and Adoption

Following its establishment in the late 19th century, the American Wire Gauge (AWG) transitioned from a manufacturer-specific system to a widely accepted North American standard through regulatory integration and industrial expansion. The system was further formalized through early 20th-century publications by the National Bureau of Standards (now NIST) and refined in 1961 by the American Society for Testing and Materials (ASTM), which extended the range to 40 AWG and adjusted finer sizes for precision. By the 1920s, as electrification spread to residential and commercial buildings, AWG was incorporated into the () for specifying conductor sizes in building wiring applications. The 1920 edition of the , for instance, required stranded conductors for sizes No. 6 B&S gauge (equivalent to AWG) and larger in conduit work, reflecting growing emphasis on safe and standardized installations amid rising electricity demand. This integration solidified during the 1930s and 1940s with revisions supporting the era's infrastructure boom, including the widespread use of non-metallic sheathed cables like Romex for interior wiring. After , AWG gained dominance in key U.S. industries amid postwar economic growth and technological innovation. In the automotive sector, standards from the Society of Automotive Engineers (SAE), such as J1128 for low-voltage primary cable, adopted AWG to specify wire sizes for vehicle electrical systems, enabling efficient production scaling. Similarly, applications under specifications like MIL-W-5086 leveraged AWG for lightweight, reliable wiring in and missiles, while the burgeoning incorporated it into component manufacturing for consistency in . This period marked AWG's shift to a across these sectors, driven by the need for interoperable parts in . Updates to AWG specifications from the 1970s through the 2000s addressed emerging needs in wire construction and performance. The rise of flexible cabling in prompted refinements for stranded wire, with ASTM B258 extending nominal cross-sectional areas to include multi-strand configurations while maintaining compatibility with solid wire equivalents. In high-frequency applications, such as RF cables for , AWG sizing was adapted to account for and impedance, as seen in standards where center conductor diameters followed AWG but with adjusted stranding for . These evolutions, including revisions to ASTM B258 in 2002 and 2014, ensured AWG's relevance in compact, high-performance systems.

Calculation and Specifications

Diameter and Area Formulas

The American Wire Gauge (AWG) system defines wire diameters through a that ensures consistent reduction ratios during manufacturing. The diameter dnd_n in inches for a given gauge number nn (where nn ranges from -3 for 4/0 AWG to 36 for #36 AWG) is calculated using the formula dn=0.005×9236−n39,d_n = 0.005 \times 92^{\frac{36 - n}{39}}, where 0.005 inches is the reference for AWG 36, and the exponent reflects the logarithmic scaling across 39 reduction steps from AWG 4/0 ( 0.460 inches) to AWG 36. These formulas are standardized in ASTM B258 and NIST Handbook 100. This progression originates from the wire-drawing process, in which metal rods are pulled through a series of conical dies to reduce incrementally; the total ratio of 92 (0.460 / 0.005) is distributed evenly over 39 dies, yielding a per-step reduction factor of 921/39≈1.122992^{1/39} \approx 1.1229. For gauges beyond this range, such as AWG 0000 (n = -3) or finer sizes, the formula extends by adjusting nn accordingly (e.g., n = -(m-1) for m/0 gauges). The cross-sectional area AnA_n, which is critical for electrical properties, follows directly from the since An=π(dn/2)2A_n = \pi (d_n / 2)^2. Substituting the gives An=Aa×9236−n19.5,A_n = A_a \times 92^{\frac{36 - n}{19.5}}, where AaA_a is the reference area for AWG 36 (≈1.96×10−5\approx 1.96 \times 10^{-5} square inches or 0.0127 mm²), and the denominator 19.5 arises from doubling the exponent for area (as area scales with the square of ). This results in the cross-sectional area approximately doubling every three gauge steps toward thicker wires (lower n), since (921/39)6≈2(92^{1/39})^6 \approx 2 for the area scaling factor over six steps, but more precisely, the per-step area ratio is 922/39≈1.260992^{2/39} \approx 1.2609, requiring about three steps for a factor of 2. Areas are often expressed in circular mils (1 circular mil = area of a circle with 0.001-inch , so An=(dn×1000)2A_n = (d_n \times 1000)^2 circular mils, where dnd_n is in inches) for convenience in electrical calculations. Electrical resistance RR of an AWG wire is inversely proportional to its cross-sectional area, given by R=ρL/AnR = \rho L / A_n, where ρ\rho is the material's resistivity, LL is the length, and AnA_n is the area. For , the standard resistivity at 20°C is 1.724×10−81.724 \times 10^{-8} Ω·m (based on the International Annealed Copper Standard). Substituting the area formula yields R∝922(n−36)39R \propto 92^{\frac{2(n - 36)}{39}}, emphasizing how resistance increases exponentially with higher gauge numbers due to diminishing area. This relation underpins AWG's utility in predicting wire performance without tabulated values.

Rules of Thumb for Estimation

Practitioners often rely on simple heuristics to estimate wire properties in field settings without precise calculations. One common approximation for involves noting that increasing the AWG number by 6 approximately halves the wire in inches; conversely, decreasing by 6 doubles it. For instance, starting from 18 AWG at approximately 0.040 inches, 12 AWG would be roughly 0.080 inches. This stems from the in the AWG system, where the ratio per gauge step is about 1.1229, leading to a doubling every 6 steps. For cross-sectional area, a useful rule is that every 3-gauge increase in AWG halves the area, while every 3-gauge decrease doubles it. This directly follows from the area being proportional to the square of the , so the 6-gauge doubling in diameter equates to a 3-gauge quadrupling in area for larger wires (or halving for smaller). As an example, 10 AWG has about four times the area of 16 AWG, aiding quick assessments of current-carrying capacity or resistance. Ampacity estimation for wires in can use the conservative guideline of 700 circular mils per . For 14 AWG, with 4,110 circular mils, this suggests roughly 6 amps, though actual household branch circuits rate it at 15 amps under limits for safety. This rule provides a safe margin for bundled or enclosed installations but underestimates for free-air or short runs.

Wire Size Data

Solid Wire Tables

The solid wire tables establish the baseline specifications for single-strand, round electrical conductors under the American Wire Gauge (AWG) system, serving as a reference for dimensions, cross-sectional areas, and material weights. These values are essential for ensuring compatibility in electrical applications, with diameters and areas standardized to facilitate precise and usage. For conductors, weights are calculated using a of 8.96 g/cm³ at 20°C, while aluminum equivalents follow the same geometric specifications but adjusted for a of 2.70 g/cm³, yielding approximately 30.1% of the weight per unit length. Diameters for solid wires are subject to manufacturing tolerances defined in relevant ASTM specifications. The following table presents key data for solid copper wire across the full AWG range from 0000 to 40, with representative examples highlighting the progression from large power conductors to ultra-fine wires; full datasets align with these standards. For instance, 12 AWG exemplifies a common building wire size with a of 0.0808 inches (2.053 mm), cross-sectional area of 6,530 circular mils (3.31 mm²), and of 19.8 lb/1,000 ft (29.5 kg/km). Aluminum weights for the same sizes are derived proportionally, such as 6.0 lb/1,000 ft (8.9 kg/km) for 12 AWG.
AWGDiameter (inches / mm)Area (circular mils / mm²)Copper Weight (lb/1,000 ft / kg/km)Aluminum Weight (lb/1,000 ft / kg/km)
00000.4600 / 11.68211,600 / 107.2641 / 954193 / 288
0000.4096 / 10.41167,800 / 85.0508 / 756153 / 228
000.3648 / 9.27133,100 / 67.4403 / 600121 / 181
00.3249 / 8.25105,600 / 53.5319 / 47596.2 / 143
10.2893 / 7.3583,690 / 42.4254 / 37776.4 / 114
20.2576 / 6.5466,360 / 33.6201 / 29960.5 / 90.1
40.2043 / 5.18941,740 / 21.1127 / 18938.2 / 56.9
60.1620 / 4.11526,240 / 13.379.7 / 11924.0 / 35.7
80.1285 / 3.2616,510 / 8.3750.0 / 74.515.1 / 22.5
100.1019 / 2.5910,380 / 5.2631.4 / 46.89.46 / 14.1
120.0808 / 2.056,530 / 3.3119.8 / 29.55.96 / 8.87
140.0641 / 1.634,110 / 2.0812.4 / 18.53.75 / 5.58
160.0508 / 1.292,580 / 1.317.81 / 11.62.35 / 3.50
180.0403 / 1.021,620 / 0.824.92 / 7.321.48 / 2.20
200.0320 / 0.8131,020 / 0.523.09 / 4.600.932 / 1.39
220.0253 / 0.643642 / 0.321.95 / 2.900.587 / 0.874
240.0201 / 0.511404 / 0.201.22 / 1.820.369 / 0.549
260.0159 / 0.404254 / 0.130.769 / 1.140.232 / 0.345
280.0126 / 0.320158.4 / 0.0800.478 / 0.7120.144 / 0.214
300.0100 / 0.254100 / 0.0510.301 / 0.4480.0907 / 0.135
320.0080 / 0.20363.0 / 0.0320.189 / 0.2820.0570 / 0.0849
340.0063 / 0.16039.7 / 0.0200.119 / 0.1770.0359 / 0.0534
360.0050 / 0.12725.0 / 0.0130.075 / 0.1120.0226 / 0.0336
380.0040 / 0.10215.7 / 0.00800.047 / 0.0700.0142 / 0.0211
400.0031 / 0.0799.6 / 0.00490.030 / 0.0450.0090 / 0.0134
To illustrate the differences in larger wire sizes and the progression of the AWG system, consider 2 AWG and 2/0 AWG (also denoted as 00 AWG) solid copper wires. The 2 AWG wire has a diameter of 0.2576 inches (6.54 mm), cross-sectional area of 66,360 circular mils (33.6 mm²), DC resistance of approximately 0.156 ohms per 1,000 ft, and ampacity ratings of 95 A at 60°C, 115 A at 75°C, and 130 A at 90°C insulation temperature. In comparison, 2/0 AWG has a diameter of 0.3648 inches (9.27 mm), area of 133,100 circular mils (67.4 mm²), resistance of approximately 0.078 ohms per 1,000 ft, and ampacity of 145 A at 60°C, 175 A at 75°C, and 195 A at 90°C. These values demonstrate that 2/0 AWG, with roughly double the cross-sectional area of 2 AWG, offers lower resistance, reduced voltage drop, and higher current-carrying capacity, making it suitable for high-power applications such as battery banks and inverters, while 2 AWG is appropriate for moderate loads like subpanels. Ampacities are based on NEC guidelines for conductors in raceway or cable and may require derating based on installation conditions, insulation type (e.g., THHN/THWN), ambient temperature, and bundling.

Stranded Wire Tables

Stranded conductors in the American Wire Gauge (AWG) system are formed by twisting multiple smaller-diameter wires into a bundle, providing greater flexibility and resistance to from or repeated bending while maintaining the same total cross-sectional area as a solid conductor of the same AWG size. The AWG designation for stranded wire is calculated based on the sum of the circular mils from all individual strands, ensuring equivalent conductivity to the solid wire baseline. Common configurations include 7-strand for fine-wire applications, featuring one central strand surrounded by six helically laid outer strands in a concentric , and 19-strand for medium-wire sizes, which adds two additional layers around the 7-strand core for enhanced flexibility. These arrangements are standardized for conductors and extend up to larger sizes like 1000 kcmil, where configurations may include 37, 61, or more strands depending on the required flexibility. Stranded wire tables specify key parameters such as the overall AWG size, number of strands, individual strand , overall bundle , and total circular mils to facilitate selection for specific applications. For instance, a 7-strand 18 AWG conductor typically uses 26 AWG strands with an overall of approximately 0.048 inches, while a 19-strand version uses finer strands around 0.0100 inches in for an overall of about 0.045 inches. Due to the air gaps in stranding, the packing efficiency results in approximately 91% of the area relative to a wire of the same overall , though the total content matches the AWG equivalent. Stranded wires of the same AWG have nearly identical DC resistance to wires, with a slight increase (~1-2%) due to the helical lay length of strands. Below is a representative table of common stranded configurations for sizes from 26 AWG to 10 AWG, based on concentric stranding.
AWG SizeStrands (Configuration)Strand Diameter (inches)Overall Diameter (inches)Circular Mils (approx.)DC Resistance (ohms/1000 ft, approx.)
267 (7/34)0.00600.018927836.5
2619 (19/38)0.00400.020030433.4
187 (7/26)0.01590.04801,7785.82
1819 (19/30)0.01000.04501,9005.51
147 (7/22)0.02530.07604,4942.25
1419 (19/26)0.01590.07204,8222.10
107 (7/18)0.04030.121011,3680.92
1019 (19/22)0.02530.114012,1780.86
Data adapted from standard concentric stranding charts; actual values may vary slightly by manufacturer. Ampacity ratings align with NEC guidelines for the total copper area, with solid and stranded conductors of the same AWG rated equivalently. Recent advancements in high-flex stranded designs, particularly for robotics and electric vehicles, incorporate finer strand counts under 2024 UL and SAE standards to withstand millions of bend cycles. For instance, 26 AWG 19-strand configurations are commonly specified for high-flex applications in robotic arms and EV charging harnesses, offering improved fatigue resistance over traditional stranding.

Nomenclature and Usage

Terms and Abbreviations

The American Wire Gauge (AWG) is the standard system for denoting the of electrically conducting wire in , with gauge numbers inversely related to wire . A (cmil) is a unit of area equal to the cross-sectional area of a circle with a of one mil (0.001 inch), commonly used to express the of wire conductors in . For larger conductors exceeding 4/0 AWG, sizes are denoted in kcmil (thousand s), which replaced the older abbreviation MCM (also thousand s) to avoid confusion with . Common abbreviations in AWG contexts include THHN (thermoplastic-insulated, heat-resistant, nylon-coated) and THWN (thermoplastic-insulated, heat- and moisture-resistant, nylon-coated), which specify insulation types for building wires rated for various environments and directly reference AWG sizes for conductor dimensions. Nomenclature in AWG has shifted from the earlier B&S gauge ( gauge), which is equivalent to modern AWG for wire sizing, to the standardized AWG designation. For sizes between 1/0 and 4/0 AWG, the fractional notation uses "aught" in written form, such as 2/0 denoting "two aught." This notation is used for wire sizes larger than 1 AWG, where the number of zeros indicates increasing size; for example, 2/0 AWG is thicker than 2 AWG, with a diameter of approximately 0.365 inches (9.27 mm) and a cross-sectional area of 67.4 mm² (133,100 circular mils), compared to 2 AWG's diameter of 0.258 inches (6.54 mm) and area of 33.6 mm² (66,360 circular mils). This roughly doubles the conductive material in 2/0 AWG, enabling it to carry higher currents with lower resistance. In USB Type-C cable specifications, 28 AWG is often used for high-speed data wire pairs in passive cable assemblies to ensure signal integrity.

Pronunciation and Regional Variations

In the electrical trade, American Wire Gauge (AWG) sizes are typically pronounced by stating the gauge number followed by "gauge" for sizes from 1 to 36, such as "ten gauge wire" for 10 AWG or "twenty-three gauge wire" for 23 AWG. This convention simplifies verbal communication among professionals when specifying wire diameters for applications like residential wiring or industrial cabling. For larger wire sizes beyond 1 AWG, which are denoted with zeros (e.g., 1/0, 2/0), the term "aught" is commonly used to pronounce the zero, resulting in expressions like "one aught wire" for 1/0 AWG or "two aught wire" for 2/0 AWG. Alternatively, some practitioners substitute "oh" for "aught," leading to pronunciations such as "two oh wire," though "aught" remains prevalent in technical contexts like and power distribution. Within the electrical trade, AWG sizes are often referenced shorthand in relation to their typical ampacity ratings and uses, such as "fourteen gauge for lights" to indicate 14 AWG wire suitable for 15-amp lighting circuits under the . Informal like "twelve wire" may also emerge in field discussions to denote 12 AWG without the full "gauge" suffix, streamlining conversations during installations. Regional differences in can influence these pronunciations subtly; for instance, "aught" is more traditional in the U.S. South, while Canadian electricians may favor "oh" in bilingual or metric-influenced settings, reflecting adaptations alongside millimeter-squared equivalents.

Comparisons and Applications

International Gauge Comparisons

The American Wire Gauge (AWG) system, primarily used in , differs from international standards that often rely on metric measurements of cross-sectional area rather than diameter-based gauges. This can complicate cross-border applications in electrical and industries, where precise equivalences are needed for compatibility, safety, and . Conversions between AWG and metric units are approximate due to the logarithmic nature of AWG steps, but they enable practical substitutions in global manufacturing and installation. For metric comparisons, AWG sizes are commonly converted to square millimeters (mm²) of cross-sectional area, which is the standard in most countries outside . For instance, 14 AWG corresponds to approximately 2.08 mm². The following table provides conversions for 10 common AWG sizes used in wiring and , based on data:
AWG (mm)Area (mm²)
240.5110.205
220.6440.326
200.8120.518
181.020.823
161.291.31
141.632.08
122.053.31
102.595.26
83.268.36
64.1113.3
These values represent nominal cross-sections for bare conductors and may vary slightly with insulation or stranding. In comparison to the British Standard Wire Gauge (SWG), also known as the Imperial Standard Wire Gauge, AWG features finer incremental steps between sizes, allowing for more precise sizing in applications like . For example, 16 AWG has a of 0.0508 inches (1.291 mm), while SWG 16 measures 0.064 inches (1.626 mm), making SWG wires thicker for the same gauge number. This difference arises from distinct historical developments: AWG follows a based on 92% area reduction per three steps, whereas SWG uses a linear inch-based scale established in the UK. Such variances require careful cross-referencing in involving legacy British Commonwealth markets. AWG is not directly equivalent to the International Electrotechnical Commission (IEC) standard 60228, which specifies nominal conductor cross-sections in mm² (e.g., 1.5 mm², 2.5 mm², 4 mm²) for global harmonization in power and control cables. For instance, 12 AWG at 3.31 mm² approximates the IEC 4 mm² size but falls short, potentially affecting current-carrying capacity ratings in metric-based systems. IEC 60228 prioritizes cross-sectional area for ampacity calculations, independent of gauge numbering, which underscores the need for conversion tools in multinational projects. In the 2020s, ongoing harmonization efforts have facilitated greater acceptance of AWG in regulations for electronics exports under the Directive. This includes harmonized approval (HAR) standards for cables that bridge North American and requirements, enabling U.S.-sourced components using AWG to align with metric equivalents for compliance testing and certification, reducing barriers in global supply chains for electrical equipment.

Practical Applications in Wiring

In electrical installations governed by the (), American Wire Gauge (AWG) sizes are primarily selected based on the allowable , which represents the maximum current a conductor can carry continuously without exceeding its insulation rating. For conductors rated up to 2000 volts and not more than three current-carrying conductors in a raceway or cable, Table 310.15(B)(16) provides the baseline ampacities. For instance, 12 AWG wire has an of 20 A at 60°C insulation (common for older thermoplastic insulations like TW), 25 A at 75°C (for types like THWN), and 30 A at 90°C (for cross-linked types like XHHW). However, protection devices for such conductors are limited by 240.4(D) to 15 A for 14 AWG, 20 A for 12 AWG, and 30 A for 10 AWG to prevent overheating. Ampacities require derating adjustments for environmental and installation conditions to ensure safety and prevent insulation degradation. For ambient temperatures above 30°C (86°F), correction factors from Table 310.15(B)(2)(a) are applied; at 45°C (113°F), the factor is 0.82 for 75°C-rated conductors, reducing the 12 AWG ampacity from 25 A to approximately 20.5 A. When more than three current-carrying conductors are bundled in a raceway or cable, adjustment factors from Table 310.15(B)(3)(a) further reduce —for 4–6 conductors, an 80% factor applies, dropping the 12 AWG 75°C rating to 20 A. These derating rules are critical in applications like conduits with multiple circuits or in hot climates, where failure to adjust can lead to and fire hazards. Beyond , wire selection considers to maintain equipment performance and efficiency, with Informational Notes in sections 210.19(A)(1) and 215.2(A)(1) recommending no more than 3% drop on circuits or feeders and 5% total from the service to the farthest outlet. For a 120 V circuit over 100 feet with a 15 A load, this may necessitate upsizing from 14 AWG (which could exceed 3% drop) to 12 AWG or larger to keep the drop under 3.6 V. Mechanical factors also influence choice; for example, in conduits, a minimum and pull strength require at least 14 AWG for non-metallic sheathed cable (NM) to avoid damage during installation. Common applications span residential, vehicular, and low-power systems. In building wiring, 14 AWG is standard for 15 A and receptacle circuits in bedrooms and general areas, while 12 AWG serves 20 A or outlets, and 6 AWG handles 60 A subpanels or dryers, all per limits and circuit requirements in Article 210. For larger installations, 2 AWG copper wire, with an ampacity of 115 A at 75°C for THHN/THWN-2 insulation, is used for moderate loads such as 100 A subpanels or feeders to HVAC systems, while derating must be applied for conditions like high ambient temperatures or bundled conductors. Similarly, 2/0 AWG, offering 175 A at 75°C, is suited for high-power applications like service entrances, battery banks, and inverters in solar or backup power systems, where its approximately double cross-sectional area compared to 2 AWG reduces resistance and voltage drop but requires derating for installation factors to ensure safe operation. Automotive wiring typically uses 18–10 AWG stranded for flexibility; 18–16 AWG for signal lines to sensors and injectors, 14–12 AWG for and power to accessories like radios, and 10–8 AWG for high-amperage grounds and starter circuits. In , finer 22–30 AWG wires are employed for low-current signals in circuit boards, sensors, and control panels, where space constraints and minimal power (under 5 A) prioritize thin diameters over high . Emerging applications in , particularly solar photovoltaic (PV) systems, reflect 2023 revisions in Article 690 that enhance conductor sizing for higher voltages and currents while improving safety. PV source circuits from modules commonly use 10 or 12 AWG PV wire for ampacities up to 30 A, but larger 6 AWG is required for output circuits in residential arrays exceeding 50 A to accommodate and voltage drops in long rooftop runs. These updates include refined grounding rules (690.43) for equipment bonding to mitigate shock risks and mandatory rapid shutdown labeling (690.12) for safety, addressing gaps in prior codes for utility-scale integrations.
Example Ampacities for Copper Conductors (NEC Table 310.15(B)(16), 75°C Column)
AWG SizeAmpacity (A)Typical Use Example
142015 A circuit
122520 A receptacle circuit
103530 A dryer circuit
66560 A subpanel or PV output
2115100 A subpanel or HVAC feeder
2/0175Service entrance or battery bank
Note: Values assume ≤3 conductors; apply as needed. limited per 240.4(D). In building wiring applications, a direct comparison of #6 AWG and #4 AWG copper conductors with THHN insulation highlights differences in physical size and current-carrying capability for higher-load circuits. #4 AWG provides greater ampacity but is larger in diameter, affecting conduit sizing and installation costs.
Specification#6 AWG#4 AWG
Bare Conductor Diameter≈0.162 inches (4.115 mm)≈0.204 inches (5.189 mm)
Overall Diameter (THHN)≈0.25 inches (6.35 mm)≈0.32 inches (8.13 mm)
Ampacity (90°C, dry locations)75 A95 A
Ampacity (75°C)65 A85 A
THHN insulation is rated 90°C in dry locations and 75°C in wet locations (THWN-2 is rated 90°C in wet locations). Ampacities are per NEC Table 310.15(B)(16) for copper conductors (≤3 current-carrying conductors in raceway/cable, 30°C ambient). Actual ampacity requires derating for ambient temperature, number of conductors, terminal temperature limits (often 75°C), and other conditions.

References

  1. https://nvlpubs.nist.gov/nistpubs/Legacy/hb/nbshandbook100.pdf
  2. https://www.astm.org/b258-18.html
  3. https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular31e2.pdf
  4. https://www.govinfo.gov/content/pkg/GOVPUB-C13-0623ad8ee79f1b1d92b7a3d7465714eb/pdf/GOVPUB-C13-0623ad8ee79f1b1d92b7a3d7465714eb.pdf
  5. https://www.engineeringtoolbox.com/awg-wire-gauge-d_731.html
  6. https://www.astm.org/Standards/B258.htm
  7. https://www.nema.org/membership/products/mw-1000
  8. https://code-authorities.ul.com/wp-content/uploads/2014/04/WC_MG.pdf
  9. https://www.elandcables.com/the-cable-lab/faqs/faq-what-is-the-conversion-between-awg-and-the-metric-system
  10. https://www.nema.org/blog/view/2019/05/19/the-1920-national-electrical-code
  11. https://www.wireharness-taiwan.com/en-US/newsc37-a-comprehensive-guide-to-international-automotive-wire-standards-awg-avss-and-beyond
  12. https://apps.dtic.mil/sti/tr/pdf/ADA617071.pdf
  13. https://timesmicrowave.com/wp-content/uploads/2022/06/tl-16-complete-catalog-r.pdf
  14. https://www.powerstream.com/Wire_Size.htm
  15. https://www.engineersedge.com/copper_wire.htm
  16. https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/
  17. https://www.iewc.com/resources/technical-guide/strand-charts
  18. https://www.calmont.com/wp-content/uploads/calmont-eng-wire-gauge.pdf
  19. https://www.romtronic.com/robot-wire-harness-standards-and-certifications-you-should-know/
  20. https://projects.coned.ncsu.edu/ncems/pdf/Glossary-2024.pdf
  21. https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70
  22. https://www.nema.org/docs/default-source/products-document-library/NEMA-Field-Rep-Training-Module-on-Electrical-Conductors-2019.pdf
  23. https://www.rose-hulman.edu/class/ee/HTML/ECE471/PDFs/Lect03.pdf
  24. https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-20
  25. https://www.lincolnelectric.com/en/welding-and-cutting-resource-center/weld-solutions/selecting-the-proper-size-welding-cables
  26. https://www.victronenergy.com/upload/documents/AWG%20to%20Metric%20Conversion%20Chart.pdf
  27. https://www.engineeringtoolbox.com/swg-standard-wire-gauge-d_1779.html
  28. https://internationalconfig.com/documents/2014-Catalog/International_Configurations_European_UL_CSA_VDE_Listed_Cordage_Hook-Up_Wire_and_Strain_Reliefs.pdf
  29. https://www.helukabel.us/HELUKABEL/Publications/Technical-Documents/Allowable-Ampacity-Tables.pdf
  30. https://usawire-cable.com/wp-content/uploads/nec-ampacities.pdf
  31. https://expertce.com/learn-articles/acceptable-voltage-drop-nec-code/
  32. https://sartellelectrical.com/standard-residential-electrical-wiring/
  33. https://www.delcity.net/electrical-wire-size-chart/
  34. https://extension.umd.edu/resource/working-solar-wiring-and-fusing-eb-2023-0676
  35. https://www.greenlancer.com/post/2023-nec-solar
  36. https://www.wireandcableyourway.com/thhn-thwn-2
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