When you are doing HST's you always add 7/8" to the finished size block. So say you want a 5" finished and you are cutting HST's you would add 7/8" to that and cut your block out 5 7/8". If you're doing QST's you would add 1 1/4" to the finished size and then cut into quarters.
Does this make sense?
A lot of individuals won't mess with the say 5 3/8", they would make it 5 1/2" - 6" and resize it down to the 4 1/2" when squaring up.
What pattern are you using, maybe someone can come up with a solution for you?