Dingle

I'm wanting to make a king size quilt using 8 packs of charm squares that have 42 in each pack. I want to put sashing between each square, either 1" or 2". I can't seem to get this figured out. Do I have enough packs or will I need more? How many across and down. I like my quilts to hang down the sides without having huge borders. Any help is appreciated.

Thanks