Wire Gauge Size & Amperage Capacities

The gauge of wire determines the amps that can flow through it.
The gauge of wire determines the amps that can flow through it. (Image: electrical wires image by jimcox40 from Fotolia.com)

Electrical wiring for homes can vary in size, which is measured as gauge. Gauge measurements go from zero to 40, with some thicker sizes: 00, 000 and 0000. The lower the number, the thicker the wire and the higher the amps.

Wire Measurement

American Wire Gauge is the standard measurement for non-iron wire in North America. The standard was developed in 1853 J.R. Brown and Sharpe company. The standard goes from 0 to 40, with thicker gauges measured as 0, 00, 000 and 0000. The numbers came from the standard manufacturing process of the 19th century that measured the number of dies the wire had to be pulled through to reduce the size.

Wire gauges are based on thickness of wire.
Wire gauges are based on thickness of wire. (Image: spools with a wire image by Victor M. from Fotolia.com)


Amperage, or ampacity, is the measure of current going through the wire. The higher the gauge of the wire, the more capacity for it to carry current. Higher gauge wires are used to distribute electricity over distance while lower gauges are used in the home.

Copper vs. Aluminum Wiring

The type of material in a wire affects amperage capacity. Copper and aluminum are the two most common materials used. Copper wiring is stronger, better over long distances and has more amperage capacity. Aluminum wiring is lighter and cheaper, but less strong and carries fewer amps.


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