not specified switching tropologoly ,switching method SPWM,SQUARE WAVE.you have planned for this inverter.
if you using push-pull with square wave tropology.core type num 16(CRGO) with stack size come to 4" is suitable for this design.
wire size required for the primary side wire swg~=9 or double layer=13 swg
Secondary wire size ~19/20 swg
turns required for this is calculated by the equation T/V=10EXP8/(4 X f x A xB) Where A= cross-sectional area in inches
B= 85000 for Crgo lamination
primary turns =12-0-120 side(push pull) -12 X T/V -0 -12 X T/V
seconadry volt= 220 X T/V