#6
A #3 copper conductor will do the job.
Might depend on your local codes, but here it is 6 AWG wire. <<>> A #4 copper conductor will limit the voltage drop to 2% or less when supplying 60 amps for 100 feet on a 230 volt system.
A 2/0 aluminum conductor, with an insulation factor of 90 degrees C, when supplying 100 amps for 200 feet on a 240 volt system, will work.
# 6 AWG (american wire gauge)
A 300 MCM aluminum conductor will limit the voltage drop to3% or less when supplying 100 amps for 400 feet on a 240 volt system.
A 250 MCM copper conductor will limit the voltage drop to 3% or less when supplying 100 amps for 300 feet on a 120 volt system.
40-100 or so
See Table NEC 310.16 but #6 copper is safe.
#6 wire stranded
I would run 1/0 gauge.
Service entrance wire size is AWG # 3 copper.