ok so like this example for Stan's VIC Transformer core?
tw = 1.09728 cm
hw = 4.72186 cm
bf = 6.25348 cm
tw = 1.09728 cm
A = ( hw * tw ) + (2( bf * tf))
A = ( 4.72186 * 1.09728 ) + (2( 6.25348 * 1.09728 ))
A = ( 5.181203 ) + (2( 6.86182 ))
A = ( 5.181203 ) + ( 13.72364 )
A = 18.904843 cm2
2 * 18.904843 = 37.809686 .....I multiplied by 2 since there are 2 core halves
37.809686 * 0.0001 = 0.0037809686 meter2
Flux = 0.3 * 0.0037809686
Flux = 0.0011343
Primary Turns = ((12V / 0.0011343) / 5000)
Primary Turns = 10579.21185 / 5000
Primary Turns = 2.1158