Another way to express this rule of thumb is that the average baby takes 2 or 3 ounces of formula each day for every pound of body weight, up to a maximum of 32 ounces. A newborn weighing 7 lbs. will take an average of 14-21 ounces of formula in a day. A 4-month-old weighing 14 pounds needs 28-32 ounces.