What does a wire gauge tell you?

A wire gauge tells you the conductor's physical size, its cross-sectional area, and from that everything electrical follows: how much current it carries safely, how much it resists, and how much voltage it loses per foot.

The AWG number runs inverse to size, a leftover from how many times the wire was drawn through dies; more draws, thinner wire, higher number.

Each step changes area by about 26 percent, and a drop of three gauge numbers doubles the copper.

What gauge does not tell you: insulation temperature rating, wet-location suitability, or whether the conductor is copper or aluminum, and all three change what the wire may actually do. Gauge is the start of the spec, not the whole of it.

The wire gauge calculator expands any gauge into diameter, resistance, and ampacity.