How do you convert wire size to amps for 240 volt?

For USA, Canada and countries running a 120/240 volt 60 Hz power supply service and also for countries in Europe and other world areas running a 230 volt 50 Hz power supply service.

There is no conversion, wire size is based on the load current of the circuit. It is stated in the electrical code books what the maximum capacity of each conductor size will allow. The voltage is independent of the wire size. When discussing voltage it is the insulation factor that you have to be concerned about. The applied voltage to a wire should never be more that the insulation factor. Common insulation voltages of most used wires are 300, 600 and 1000 volts.

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.