Off the top of my head, I think it would end up being a 4" block, don't you think? After you sew both opposite sides of your two 5" charm squares together with 1/4" seams on opposing sides, that leaves you with 4-1/2". When cut horizontally across the middle of the block at 2-1/2", then you press the seams open, you should have 4-1/2" blocks. At least, that's what I think. I'll turn this subject over to my engineer hubby for a definite answer.