What size copper wire is need to feed a 100 amp subpanel located 6 feet from a 200 amp main panel?

For a 100 amp subpanel located 6 feet from a 200 amp main panel, you would typically use #3 AWG copper wire. This size is adequate for carrying the load while minimizing voltage drop over the short distance. It's always recommended to consult local electrical codes or a licensed electrician to ensure compliance and safety.