What gauge wire must be used for a 20 AMP circuit?

For a 20 AMP circuit, the appropriate wire gauge is 12 gauge. This is because the National Electrical Code (NEC) specifies that 12 gauge wire is rated for a maximum of 20 amps, making it suitable for use in residential and commercial electrical applications where a circuit is intended to carry this load.

Using a wire gauge that is too small for the ampacity can lead to overheating and potential fire hazards. The selection of the proper wire gauge also ensures that voltage drop is kept within acceptable limits over the distance the circuit runs.

Wire gauges larger than 12, such as 10 gauge, are typically used for higher current loads, while smaller gauges like 14 and 16 are inappropriate for a 20 AMP circuit, as they are rated for lower amperages (14 gauge for 15 amps and 16 gauge for even less). Therefore, 12 gauge wire is the standard and safe choice for ensuring the circuit operates efficiently and safely at 20 amps.