AWG, or American Wire Gauge, is the standard system utilized by Canada and the United States. The gauge of a wire is influenced by the diameter of the wire. The larger the diameter of the wire, the more current the wire can handle, but the lower the gauge size. The metric gauge standard is factored by the diameter of the wire in millimeters, and as with all metric, uses a base-10 scale. Unlike the AWG scale, the larger the diameter measured, the higher the gauge number for the wire.
Cut off the power connected to the wire.
Place the wire into a wire stripper's hole. The hole should be just a little smaller than the wire. Clamp down on the handle of the wire strippers to cut away the insulation. Pull the insulation from the wire.
Place the wire into the wire stripper's hole that is the closest in size. If a gap is present, then the hole is too big.
Read the number next to the hole to determine the gauge size of the wire.
Write the number down and the color of the insulation if you are working with several wires.