The common size for a crib mattress is 27” by 52” so a lot of quilters will tell you the size of the quilt should be 36” by 60”. This would require a pre cut batting of 45” by 60”.
Other quilters using blocks to create a crib or baby quilt like the size 38” by 48”. If you are using blocks to cover just your mattress top and will be adding a border the number of blocks needed depends on the size of the block. For example
BLOCK SIZE # OF BLOCKS NEEDED THE LAYOUT
4” 84 6 X 8
6” 40 5 X 8
8” 24 4 X 8
9” 15 3 X 5
10” 15 3 X 5
12” 8 2 X 4
