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The table below lists the wire Characteristics for different gauges of the American Wire Gauge [AWG]. The American Wire Gauge provides a means of specifying wire diameters. For each different AWG [wire size] the table provides the Diameter [in mils], the resistance per 1000 foot, the current carrying capability [Ampacity], and Pounds per Foot [number of feet required to weigh 1 pound].
The AWG is based upon a constant ratio of cross-section between wires of successive gage numbers.

Read the notes below the table to determine how the Ampacity was derived. The larger the AWG number, the smaller diameter wire. The table is based on an ambient temperature of 25^oC. Some of the standard wire sizes used in a number of Interface Buses [for data lines] are #22AWG, #24AWG, #26AWG, and 30AWG. A listing of Electronic bus standards are located on the Buses page. Another table near the bottom of the page provides copper current carrying ability [Ampacity] for Teflon insulated wire. Conductor size is based one or more of the following considerations:
Current carrying capacity [inducing a rise in wire temperature, in high-voltage lines], Short circuit current, or Voltage drop [long low voltage lines].

General Notes:
The wire size is different between the American Wire Gage [AWG] and the British standard. The table above only lists the AWG standard.
AWG [American Wire Gauge] may also be called the Brown and Sharpe (B&S) Wire Gauge. [note]
The Birmingham Wire Gauge [BWG] is used for steel armor wire. [other wire gauge standards]
Watch for round-off errors, as many numbers were rounded. Use the table as a guide. [Equivalent Cross-Sections of Wire]
The weight [pound per foot] does not include wire insulation. The weight of the wire is critical in some applications. More data [AWG Table for 25C - 65C]
Circular mils is the diameter squared in mils. [Table of AWG sizes in metric]
The editor has never seen the American Wire Gauge [AWG]

IEEE Standard 835, IEEE Standard Power Cable Ampacity Tables
IEEE Standard 848, Procedure for the Determination of the Ampacity Derating of Fire Protected Cables
ICEA P-54-440, NEMA Pub. No. WC 51 - Ampacities of Cables in Open-Top Trays.

The National Electrical Code [NEC] requires their own cable sizing for premises wiring. Refer to the NEC rules to determine building wiring, as this page relates to electronic equipment wiring. For reference, the ampacity of copper wire at 30⁰C for common wire sizes
14 AWG may carry a maximum of 20 Amps in free air, or 15 Amps as part of a 3 conductor cable.
12 AWG may carry a maximum of 25 Amps in free air, or 20 Amps as part of a 3 conductor cable.
10 AWG may carry a maximum of 40 Amps in free air, or 30 Amps as part of a 3 conductor cable.
8 AWG may carry a maximum of 70 Amps in free air, or 50 Amps as part of a 3 conductor cable.

The wire fusing [melting] current is based on the material the wire is made of, the diameter of the wire and the melting point of the the material. The wire fusing current of a wire is provided in tables as constant current or as [a larger] current for some given amount of time.
I found this formula used on a few different sites [un-verified]; I=Ad^(3/2) @ d is in inches, A is a constant: A = 10,244 for Copper. A = 7,585 for Aluminum.
I have listed a number of values for fusing current in the table above, for selected AWG sizes.

Aluminum wire properties are listed under on the Aluminum electrical Wire page

Manufacturers listing for Electrical Wire and Cable,
also Monel wire, and Nichrome wire
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Cable manufacturers will provide different numbers based on the insulation used for the wire.
Use the table below to off-set the conservative current carrying numbers in the table above, and the fusing current. The table below lists copper wire with a Teflon [TFE] insulation. Teflon insulation has a higher operation temperature range then other insulators, for example PVC. The table below is based on data derived from MIL-STD-975, using 70⁰C as the operating temperature. To derate based on number of wires in a bundle:
I_BW = I_SW x (29 - #_wire) / 28 @ [1 to 15 Bundled wires]
I_BW = I_SW x (0.5) @ [more then 15 Bundled wires]
I_SW = Single wire
I_BW = Bundled wires
To derate by temperature use; derate by 80% at 150⁰C, 70% at 135⁰C, or 50% at 105⁰C (per MIL-STD-975)

Refer to the How to Derate Components page for derating wire with other then Teflon insulation

I have seen one other Military Specification [MIL-STD-xx] for copper wire current capability. That standard [I did not note the standard number] listed AWG 18 [for example] as 10 amps with TFE insulation. That indicates that this additional military specification uses the same data listed in the table above, but may be listed for 25⁰C, and not 70⁰C as the table uses. So this table above has already been derated for 70⁰C.
This page provides a conservative guide for Ampacity for bare copper wire [700 Circular mils/amp] , the melting [point] current for bare copper wire, and the Ampacity for TFE coated copper wire. The American Wire Gage [AWG] for bare copper wire is also listed. Refer to the National Electrical Code [NEC] to determine cable sizing for premises wiring. This page represents my notes on the subject, purchase one of the standards or specifications referenced on this page when doing professional work.
Also see the Wire Insulation Color Code page; Color coding of wire insulation based on application.

Determine cable length vs. voltage drop. Determine cable length vs. Heat increase.

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Related technical data on Chassis Cable Design and Considerations

Technical Key words: American Wire Gage, AWG, Bare copper wire, Ampacity, Fusing, Brown and Sharpe (B&S), Wire gauge chart
Electrical Wire Sizing, Cable, Wiring, Heating, Wire size amperage chart, Electrical Code, Length, NEC, National Electrical Code.

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