The gauge of wire you need for your 220 volt circuit depends on how many amperes will be running through the wire. The higher the amperage the bigger the wire. Wire gauges run contrary to what you might think; the lower the number the thicker the wire. If you have any doubts about your amperage, go with a thicker wire. It is always best to have a licensed electrician do electrical repairs in the home.
Determine the total number of watts you will be running on the wire.
Divide the wattage by 220 (the circuit voltage) to get the number of amps. For example, if you are running 2500 watts, that would be 11.4 amps.
Use an 18 gauge wire for current of 5 amperes or less. Use 12 gauge for currents that are between 5 amperes and 11.5 amperes. Use 6 gauge for up to 30 amperes, and 2 gauge wire for current up to 50 amperes. In this example, 12 gauge wire would be sufficient.