American wire gauges and other strange units of measure for copper and aluminum
The "furlongs per fortnight" of electricity
Electrical and other wire is commonly "gauged" from 7/0 which is about a thumb's width in diameter to 60 which is about one tenth the diameter of a human hair.
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By definition, 36 AWG is 0.005 inches in diameter, and 0000 AWG is 0.46 inches (11.68 mm) 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.
Wires larger than 4/0 are commonly sized in MCM or kcmil, which is a unit of area equal to 1000 times the area enclosed by a circle 1/1000 inch in diameter.
According to Google:
Common MCM (kcmil) Wire Sizes //MCM (or kcmil) is used for large-diameter electrical cables, ranging from 250 MCM to 2,000 MCM. [KrisTech Wire] //Smallest Large Gauge: 250 MCM //Most Common/Key Sizes: 250, 300, 350, 400, 500, 600, 750, 1000 MCM
Wires 1000 MCM and larger are seriously derated for electric current carrying capacity because of the internal magnetic repulsion which causes the electric current to eddy and fight against itself and create hot spots inside the conductor regardless of its diameter or cross-sectional area.
It is not really practical at all to attempt to carry an electric current greater than about 1000 amps in a single "wire." That much current must be broken up and distributed into smaller conductors and interspersed evenly with the conductors carrying the return current, in order to avoid undesirable humming or vibration for AC currents and/or other heat- and force-inducing magnetic effects for DC currents.