Would you be cutting these squares yourself? It seems like many of the ready-cut ones are only five inches square.
If starting with 5.25 inch (5-1/4) cut size squares,
That would give you 4.75 "finished" size squares -
If you are planning to make this without borders -
11 x 4.75 = 52.25
12 x 4.75 = 57.00
13 x 4.75 = 61.75
14 x 4.75 = 66.50
11 x 13 = 123 squares
This would yield a top size of 52.25 x 61.75 inches - assuming 1/4 inch seams