How to Size Electrical Wires

A ruler is all you need to size electrical wire.

Wire gauges are classified as either American Wire Gauge or as the Metric Gauge. These gauges conform directly to the diameter of the wire size in either inches or millimeters. In the American Wire Gauge classification, wire is numbered from the thickest and heaviest, 0000-gauge, to the thinnest and lightest --- 32-gauge. Metric wire is classified at 2.0 for the thickest and heaviest, to 40 at its thinnest and lightest. Using these specifications and a wire gauge table, you can size any diameter.

Things You'll Need

• Engineering ruler
• Wire gauge table

Instructions

1. Grasp any size wire. Using an engineering ruler, measure the end diameter of the wire. It is important that you measure only the wire, or the conductor as it is called, not the surrounding insulation.

2. Convert this measurement into the wire size by referring to a wire gauge chart. As an example, a wire size measured at .46 inches converts to a 0000-gauge wire. A wire size measured at .1019 inches, or a 1/10 of an inch in diameter, converts to a 10-gauge wire.

3. Convert measurements into metric size by using the same principle. A wire measured at 11.64 millimeters converts to a 0000-gauge wire. A wire size measured at 2.58826 or 2-1/2 millimeters, is converted to a 10-gauge wire.

Tips & Warnings

• You can also size a wire using a mathematical calculation. Once you measure the wire, take that measurement, represented by the letter "D" in the American Wire Gauge, and calculate the wire gauge with this formula: D(AWG)=.005•92((36-AWG)/39).

References

• Power Stream: Wire Gauge and Current Limits
• National Fire Academy Department of Homeland Security: Using Engineer And Architech Scales

Resources

• Read this Article in Spanish