Emergency water storage calculator

Store at least 1 gallon of water per person per day for 3 days, and a 2-week supply if you can. Set up your household below to get your exact number, with pets and hot weather included.

Every number checked against CDC and Ready.gov guidance. Updated October 13, 2026. How we work

Your household needs

28gallons

About 106 liters for 2 weeks.

2 people × 14 days × 1 gallon28 gal

People at home

How long should it last?

3 days 1 week 2 weeks 1 month

Dogs, total weight

0lb

Cats

A dog drinks about 1 fl oz per pound of body weight a day. A 10-lb cat drinks about 1 cup.

Plan for very hot weather

Ready.gov: in very hot temperatures, water needs can double.

Extra cushion

None +25% +50%

For pregnancy, nursing, illness or young children. The CDC and Ready.gov say they may need more water but don't give a number, so pick a cushion you're comfortable with.

That's about

5-gallon jugs: 6
1-gallon jugs: 28
Cases of 24 bottles: 9

Price of a case of 24 bottles

Drinking waterFilled todayReplace by in 6 months

Label each container like this: the CDC suggests the words "drinking water" and the date. Replace water you fill yourself every 6 months. For store-bought water, go by the date on the bottle.

How the calculator works

Every number comes from public health guidance, and the math is shown so you can check it.

The rules behind your number
What	Rule	Source
People	1 gallon per person per day, for drinking and basic hygiene	CDC, Ready.gov
How long	At least 3 days, and 2 weeks if you can	CDC
Very hot weather	Needs can double, so the people part is doubled	Ready.gov
Extra cushion	Your choice. Pregnant or nursing women, sick people and children may need more	CDC, Ready.gov
Dogs	About 1 fl oz per pound of body weight per day	GoodRx (vet-reviewed)
Cats	About 4 fl oz per 5 lb per day. We assume a 10-lb cat, so 8 fl oz	WebVet (vet-reviewed)
Replacing	Water you store yourself: every 6 months. Store-bought: the date on the bottle	CDC, Ready.gov

The total is rounded up to the next whole gallon. A gallon of water weighs about 8.34 lb, and a case of 24 bottles of 16.9 fl oz holds about 3.2 gallons.

Quick answers for common households

At 1 gallon per person per day, before pets or hot weather:

Gallons of water to store
Household	3 days	2 weeks	1 month
1 person	3	14	30
2 people	6	28	60
3 people	9	42	90
4 people	12	56	120
5 people	15	70	150
6 people	18	84	180

A family of 4 needs 56 gallons for 2 weeks. That's about 12 five-gallon jugs, weighing around 467 lb in total.

Store it safely

Store-bought is simplest. The CDC calls unopened, commercially bottled water the safest and most reliable source in an emergency.
Use food-grade containers with tight lids if you fill your own. Never reuse a container that held chemicals like bleach or pesticides.
Skip milk and juice jugs. Ready.gov says milk proteins and fruit sugars can't be fully cleaned out and can feed bacteria. Clean 2-liter soda bottles are fine.
Keep it cool and dark: 50–70°F, out of direct sunlight, away from gasoline and pesticides.
Label every container "drinking water" with the date you filled it.

Our guide to emergency water containers compares weight, space and shelf life, and shows how to clean and fill your own.

Water you already have at home

If the taps stop, the CDC lists these sources inside your home:

The water heater tank (the one for your taps, not a home heating system)
Melted ice cubes made with clean water
The toilet tank, not the bowl, if the water is clear and has no cleaning chemicals in it
The liquid in canned fruit and vegetables

Pool and spa water can be used for washing and cleaning, but not for drinking.

Questions people ask

Does 1 gallon a day include cooking and washing?

Ready.gov's gallon a day covers drinking and sanitation. It doesn't cover flushing: a toilet that meets the federal standard uses up to 1.6 gallons per flush. Flushing water doesn't need to be drinkable, so you can store it separately.

How long does stored water last?

Replace water you store yourself every 6 months, as the CDC and Ready.gov advise. For store-bought water, go by the date printed on the bottle. The reminder button above puts the date in your calendar. More in how long stored water lasts.

Do I need to treat tap water before storing it?

If your water comes from a public system that treats it with chlorine, Ready.gov says you don't need to add anything. If it comes from a well or isn't treated, follow Ready.gov's instructions for adding bleach.

How much water does a family of 4 need for 2 weeks?

56 gallons, at 1 gallon per person per day. That's about 12 five-gallon jugs or 18 cases of 24 bottles. In very hot weather, plan for up to twice as much.

Can I store water in milk jugs?

No. Ready.gov advises against containers that held milk or fruit juice, because the proteins and sugars can't be fully removed and can encourage bacteria. Use clean soda bottles or food-grade containers instead.

How much water do pets need?

A dog drinks about 1 fl oz per pound of body weight per day, so a 50-lb dog needs roughly 3 pints. A 10-lb cat needs about 1 cup a day. Add your pets in the calculator above, or see the pet water guide.

Guides

Water storage for apartments and small spaces
How much you need, where it fits and how heavy it gets.
Emergency water containers compared
Bottles, jugs, bricks and drums: weight, space and how long they last.
How much water do pets need in an emergency?
Dogs and cats by weight, with a pet water calculator.
How long does stored water last?
When to replace it, plus printable labels for your containers.
How much emergency water do you need in a heat wave?
Why hot weather doubles your water, and the warning signs to watch for.
Where to find hidden water in your home
Your water heater, pipes and ice cubes, and how to get the water out.
Can you store emergency water in a garage or car?
Where water keeps best, and how to keep a small supply in your car.

Curious how much water is floating in the air of your home right now? Try the air water calculator.