Wire Gauge Converter

AWG (American Wire Gauge) numbers describe wire thickness, and a smaller number means a thicker wire. 12 AWG is 2.05 mm across, with a copper area of 3.31 square millimeters. This converter turns any gauge from 0000 (4/0) to 40 AWG into metric sizes and copper resistance.

The scale is set by a formula: diameter in mm = 0.127 x 92^((36 - AWG) / 39). Two handy rules follow from it. Every 6 gauges down, the diameter doubles. Every 3 gauges down, the area roughly doubles, which halves the resistance. So 10 AWG has about twice the copper of 13 AWG, and 12 AWG has about four times the copper of 18 AWG.

For each gauge, you get the diameter in millimeters and inches. You also get the area in square millimeters and in circular mils, a US unit equal to the diameter in thousandths of an inch, squared. Last is the resistance of solid copper wire at 20 C, per meter and per 1,000 feet. Stranded wire is a bit wider than solid wire of the same gauge, but it carries about the same copper area.

Resistance per length helps you estimate voltage drop, which is current times the resistance of the whole run, out and back. This tool does not give ampacity, the safe current a wire can carry. That depends on insulation, bundling and your local electrical code, so check the code tables for any building wiring. For the voltage drop math itself, use the Ohm's Law Calculator.