How much water do I need per person:
Since a normally active person needs at least one gallon of water daily just for drinking, you should store at least one gallon of water per person per day. However individual needs may vary, depending on age, physical condition, activity, diet, and climate. For instance, children, nursing mothers, sick people, or a medical emergency might require additional water. Additionally, if you live in a warm-weather climate, more water may be necessary, and in very hot temperatures, water needs can double.
To be safe and well supplied, it’s a good idea to keep at least a three-day supply of water per person.