What is the standard wiring gauge system used in the United States?

The American Wire Gauge (AWG) system is the standard used in the United States to denote the diameter of electrical wires. It is a standardized wire gauge system that helps electricians and engineers choose appropriate wire sizes for various applications based on current-carrying capacity, resistance, and other factors. The AWG system allows for a straightforward comparison of wire sizes, with smaller gauge numbers representing larger wire diameters. This system is essential for ensuring safety and efficiency in electrical installations, considering factors like voltage drop and circuit protection.

The other choices do not pertain to the standardized measurement of wire thickness in the same context. SWG refers to the British Standard Wire Gauge, which is not commonly used in the U.S. The metric system is a decimal-based system of measurement not specifically laid out for wire gauge, while THHN is a type of wire insulation rather than a measurement system. Only AWG accurately represents the standard wiring gauge system used in the United States.