Wire sizes are called gauges. The gauge of a wire is determined by the diameter of the conductor cable that is wrapped within the insulated sleeve. Different gauge wires are used for different purposes, so knowing the gauge of your wire is very important. A thinner gauge wire will carry an audio signal well but may not be thick enough to handle a large load of power. You can check the gauge of your wire with a simple fabric measuring tape.
Strip the insulation from around the wire using wire strippers if it is not already bare. The gauge of a wire is measured by the diameter of the conductor cable, not including the insulation.
Determine the diameter by wrapping the tape around the conductor wire. Record the measurement in millimeters.
Compare your measurement with a wire gauge sizing chart, such as the one found in the Resource section, to find the wire's gauge. For example, if your measurement is 1 mm, you have a 16-gauge wire.