Up to 05 amps: 18 AWG
Up to 10 amps: 16 AWG
Up to 15 amps: 14 AWG
Up to 20 amps: 12 AWG
Up to 30 amps: 10 AWG
Up to 50 amps: 8 AWG
Up to 65 amps: 6 AWG
Up to 85 amps: 4 AWG

http://www.amplepower.com/primer/gauge/

i found these on the internet and used it as a reference.