I don't know for sure if I understand what you are asking, but I will try...
If you need a 45" log cabin and you have 12 strips wide in your log cabin. 45/12=3.75 and if you add .5 for seam allowances. I come up with 4.25 or 4 1/4". Your finished square will actually be a little larger because of the white strip that connects them, so your large square would be 92.25", if I understand what you are asking.