How much

One gallon per person per day, for drinking and sanitation (Ready.gov). Plan 3 days for a go-bag and 2 weeks at home (Red Cross).

Household	3 days	2 weeks
1 person	3 gallons	14 gallons
2 people	6 gallons	28 gallons
Family of 4	12 gallons	56 gallons

A gallon is about two quarts to drink and two for food preparation and hygiene. Hot weather and hard work can double what a person drinks, and children, nursing mothers and people who are ill need more (Ready Illinois). Add water for pets.

Store-bought or your own bottles

Commercially bottled water is the simplest: keep it sealed, in a cool dark place, and use it by its date.

Bottling tap water yourself works if you do it properly (Ready.gov):

Wash plastic soda bottles with dish soap and rinse well.
Sanitize with 1 teaspoon of unscented liquid chlorine bleach in a quart of water, swirl, then rinse.
Fill to the top with tap water. Treated city water needs nothing more; well water needs two drops of unscented bleach per bottle and 30 minutes standing (Ready.gov's soda-bottle method).
Cap tightly, label with the date and store somewhere cool and dark.
Replace it every six months.

Working out bottles

A gallon is 128 fluid ounces, so 16.9 oz bottles go about 7.6 to the gallon. The calculator converts your total into jugs, bottles and cases of 24.

Containers and treatment

Sealed cases of bottled water are the simplest store. For larger amounts, food-grade water containers with taps make two weeks practical, and water purification tablets are a backup, available at most sporting goods stores, as Ready.gov notes.