Water recommendations vary by age. Kids under one year of age only need 4 to 8 oz per day. Children 1-3 years old need about 4 cups of beverages each day, primarily water and milk (limit juice). According to the Academy of Nutrition and Dietetics, boys and girls 4-8 years old need 7 cups per day. Girls and boys 9-13 years should drink 9-10 cups per day. Keep in mind this includes total water intake from water, other beverages, and foods like fruits and vegetables, so actual cups of water may be less.