What size wire do I need?
When running power and ground cable for car audio systems, it is strongly recommended that you replace all of the following lines with larger gauge cable:
motor to chassis ground
alternator to battery positive terminal
battery negative terminal to chassis ground
battery positive terminal to amplifiers or distribution block
amplifier(s) to chassis ground
power and ground cables:
For a reference chart to determine wire size based on distance run and current draw or wattage, see here:
http://www.the12volt.com/info/recwirsz.asp
For actual wire diameter based on American Wire Gauge (AWG) see here:
http://www.the12volt.com/wiring/awg.asp
These charts only go up to 2AWG, but the logical progression to 1/0, 0, and 00 gauge should be obvious.
For more information on wire and it's applications in car audio, see here:
http://www.bcae1.com/wire.htm
Speaker wire sizing:
Speaker wire size calculator