a yard of fabric is (about) 36" x 40" usable fabric---so charm squares (5") you can get 7 across (= 35") x 8 down= (40")
so...56 squares in a yard (7x8)
jelly roll strips are 2 1/2" wide---so you can get 14 strips from a yard (35" x 40")
layer cakes are 10" squares---so 3X4= 12 squares in a yard (30" x 40")