If you set them with no sashing, just block against block with no borders, you would need 56 blocks. That would give you a 84 x 92 inch quilt. However, you are probably going to want some kind of sashing and an outer border, possibly even an inner border. Which means you could get away with approx. 25 blocks with a 2" sashing.
There are so many variables, wow. This is going to be so interesting to see how everyone sets their quilts.
Jeanye