Thank you, I got my response. My husband the math wizard (I'm the speller, he is the mathematician) came along at just the right time and helped me figure out a chart I could use. I hope this helps someone, so for your edification or just in case you were interested, here is the chart:
4x4 of this size will fit a square of this size:
2.5 4.5
3 5.5
3.5 6.5
4 7.5
4.5 8.5
5 9.5
5.5 9.5
6 11.5
6.5 12.5
7 13.5
7.5 13.5
8 15.5
8.5 16.5