1 An 8-pound newborn drinks about 2 ounces at a time, roughly 10 times a day. 2  A 14-pound 4-month-old drinks 4 to 5 ounces at a time about six to eight times a day.  A 16-pound 6-month-old drinks 5 to 6 ounces at a time, roughly five times a day, in addition to eating some baby food.