Thank you all for your help in this. I knew there were some super intelligent quilters out there and that there had to be a formula for what I need. I do usually just draw everything out on graph paper, but this time I needed to know how to figure it backwards.
I'm going to be making a wedding quilt and the bride has a certain pattern in mind. It has sashed blocks on point, but her example isn't big enough for a bed quilt. I want to enlarge the block size so I won't have to make 700 small blocks to get a large queen quilt. Now I can figure out how many 8" or 10" blocks I would need to complete the pattern she's chosen.
Thanks again for all your help!