let's see... if you're wanting the squares to be 2" Finished size...
40"/2" = 20 squares across (cut at 2.5 inches)
60"/2" = 30 squares down
20x30 = 600 squares, cut at 2.5 inches.
If you add a narrow border, your quilt should finish at a nice size.
I hope my math is correct... Perhaps I should be waiting until I've had more Coffee!!! lol...