Hello,
I would need to design a board to transport 10Amps (MAX) at mains voltage 230V.
I have initially defined 2mm width traces on one side for this.
I have checked this with calculators such as:
http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/
First of all what is the default THICKNESS of a standard PCB line? (since it seems this cannot be set in EasyEDA although I can do double sided traces to double up on this with VIAs)
Is this calculator any valid for your site?
You'll find the default copper thickness for boards made by jlcpcb on the PCB order page (in terms of ounces) and here:
https://jlcpcb.com/capabilities/Capabilities
Note that if you wish to increase the current capacity of a track by soldering wires over it then you can remove the solder mask over selected tracks using the "Expose Copper" button.
Don't forget that the clearance around tracks vs. the voltage they are at is just as important as the copper width and thickness for the current they carry and the acceptable temperature rise at that current.