Just figured out the size I want to do and this is what I came up with....If a quilt is to measure let's say 50x70... that's 25 2.5" squares across for the 50" width...you need 35 2.5" squares for the 70" length...so you multiply 25x35 and you come up with 875 2.5" squares....now I know there are the odd # of squares to start off with & the sides but to round it up you need to divide the 875 by 5 to get the # of sets needed...which would be 175 sets rounded up....not pieces... I think this is right....