How Much Water to Store Per Person: Exact Amounts

The short answer, before the reasoning

Store one gallon (3.8 L) of water per person per day. Target a two-week supply at home. Treat three days as the lowest number you should ever be sitting at.

That works out to:

One adult, 3 days: 3 gallons (11 L)
One adult, 14 days: 14 gallons (53 L)
Household of four, 3 days: 12 gallons (45 L)
Household of four, 14 days: 56 gallons (212 L)

The one-gallon-per-person-per-day figure and the two-week home target both come from Ready.gov, and the American Red Cross publishes the same per-person number. It is not a Rational Survivor invention and you should not need to take our word for it.

If you store nothing else after reading this page, store 12 gallons (45 L) for a family of four. It fits under a bed. It costs less than a takeaway dinner. It is the single highest-return thing in household preparedness, and it is the one most people skip because it is boring.

Where the one-gallon figure comes from, and what it is actually covering

A gallon a day is not a hydration requirement. A sedentary adult in a mild room does not drink a gallon of water a day, and nobody at FEMA thinks they do. The figure is a household planning allowance that bundles several needs into one number that is easy to multiply.

The conventional split is roughly half and half:

About 0.5 gallon (1.9 L) for drinking. Enough for an adult in moderate conditions, with margin.
About 0.5 gallon (1.9 L) for everything else. Rehydrating food, cooking pasta or rice, washing hands, brushing teeth, cleaning a wound, wiping down a surface someone is going to eat off.

That second half is the part people forget, and it is the part that decides whether a two-week outage is merely inconvenient or becomes a gastrointestinal illness problem. CDC Emergency Preparedness is blunt about the link between disrupted water service and disease transmission: when handwashing stops, norovirus and similar pathogens move through a household fast.

For scale: a single flush of a US toilet manufactured after 1994 uses about 1.6 gallons (6 L). One flush consumes more water than a person's entire daily allowance. This is why sanitation water is planned separately from drinking water, and why you flush with pool water, rain-barrel water, bath water or snowmelt — never from your stored drinking supply. Filling a bathtub as soon as a storm is forecast is one of the cheapest preparations available, and that water is for flushing and washing, not for drinking.

Run the arithmetic for your household

The formula is trivial. The consequences of the result are not.

Gallons = people × days × 1 gallon

Work the example. A household of four, planning for 14 days:

4 × 14 × 1 = 56 gallons (212 L)

Now convert that into things you have to physically handle, because this is where plans die.

Weight. Water weighs 8.34 lb per gallon (1 kg per litre). 56 × 8.34 = 467 lb (212 kg). That is a load-bearing question, not a shopping question. Do not put it on a shelf rated for books.
Volume. One cubic foot holds 7.48 gallons, so 56 gallons is 7.5 cubic feet (0.21 m³) of water — call it 10 cubic feet (0.28 m³) once containers and stacking air are included. Roughly the interior of a small chest freezer.
In 5-gallon jugs. Twelve jugs gets you 60 gallons (227 L). Each full jug weighs about 43 lb (19.5 kg) with the container. A jug occupies about one square foot (0.09 m²) of floor and stands roughly 20 in (50 cm) tall.
In retail cases. A case of 24 × 16.9 fl oz bottles holds 3.17 gallons (12 L) and weighs about 28 lb (13 kg). You need 18 cases.
In a 55-gallon drum. One drum nearly covers it — and weighs 459 lb (208 kg) full. You will need a siphon pump, a bung wrench, and a floor you are confident about. You will never move it once filled.

If you live somewhere hot, run the same arithmetic at 2 gallons per person per day and look at the answer: 112 gallons (424 L), 934 lb (424 kg). At that point storage stops being a closet decision and becomes a treatment decision — you plan to make water, not only to hold it. That is what the second half of this guide is for.

When one gallon per person per day is not enough

The baseline assumes a healthy adult, moderate temperature, sitting still. Every deviation pushes the number up. Ready.gov names most of these explicitly.

Heat. In very hot conditions, water needs can double. A summer grid failure in Phoenix and a winter ice storm in Vermont are not the same planning problem. If your region regularly exceeds 95 °F (35 °C), plan at 2 gallons (7.6 L) per person per day.
Physical work. Clearing a fallen tree, carrying water, or walking out of an area is heavy labour. A person doing sustained work in heat can sweat well over a litre an hour. Plan work days at double, and plan to rest through the hottest hours rather than drinking your way through them.
Illness. Vomiting and diarrhoea are the fastest route to a medical emergency during an outage, particularly in children and older adults. Store oral rehydration salts alongside the water; they weigh nothing. See our wilderness first aid kit guide for how we think about the rest of that kit.
Pregnancy and nursing. Ready.gov flags nursing parents as needing more. Add a meaningful margin rather than a token one.
Infants. If you have a baby, store ready-to-feed liquid formula. It removes the water question entirely at the moment you least want to be solving it. If you use powdered formula, follow the manufacturer's and CDC's mixing instructions rather than improvising with treated water.
Altitude. Above roughly 8,000 ft (2,400 m), respiratory and urinary losses increase. Plan higher.
Pets. A common veterinary rule of thumb is about 1 fl oz of water per pound of body weight per day. A 60 lb (27 kg) dog is therefore roughly half a gallon (1.9 L) daily — add it to the household total, do not hope it fits in the margin.
Medical equipment and diets. Dialysis, certain wound care regimes, and sodium-restricted diets change the answer. That is a conversation with your clinician, not with a website. See the disclaimer.

Containers, sanitising, and rotation

Water does not spoil. Containers spoil water. Everything in this section is about the container.

Use for storage:

Commercially bottled water, unopened, kept in its original sealed container. Simplest option, and the seal is the point — do not decant it.
Food-grade HDPE containers sold for water storage: 5- to 7-gallon jugs, stackable water bricks, 55-gallon drums.
Clean 2-litre PETE soft-drink bottles, which Ready.gov specifically names as an acceptable fallback.

Do not use:

Milk jugs. Milk protein and fat residue cannot be reliably scrubbed out, and the plastic is designed to biodegrade.
Fruit juice bottles. Same problem: sugar residue feeds bacterial growth.
Containers that ever held a non-food substance. Not solvent jugs, not detergent bottles, not "it only had chemicals in it once."

To sanitise a reused bottle, wash it with soap and water, rinse thoroughly, then sanitise with a solution of 1 teaspoon of unscented liquid household chlorine bleach in 1 quart (1 L) of water. Swirl so the solution touches every interior surface, let it stand about 30 seconds, pour it out, and let the bottle air-dry or rinse it with clean water. Fill from a safe tap, cap tightly without touching the inside of the cap, and write the fill date on the outside with permanent marker.

Rotation. Replace water you bottled yourself every six months. Use commercially bottled water by its printed date. Set a calendar reminder on the 1st of a fixed month — the guides that survive contact with real life are the ones tied to a date, not to intention.

Storage conditions. Cool, dark, and away from direct sunlight, which drives algal growth in translucent containers and degrades plastic. Keep containers away from gasoline, kerosene, pesticides and solvents — polyethylene is permeable, and vapours will migrate through the wall and into the water. That, not concrete, is the real version of the old "never store water on a garage floor" advice. Leave roughly 10% headspace in containers stored anywhere that can freeze.

Split your storage across at least two locations. A single stack in the one room that floods, or a garage that reaches 120 °F (49 °C) in August, is a single point of failure.

The 40 to 80 gallons already inside your house

Before you buy anything, inventory what you already have. Most US homes contain more potable water than the occupants realise, and it is free.

The water heater tank. Typically 40 to 80 gallons (150–300 L) of potable water. This is the single largest reserve in most homes. Before draining: shut off the gas or the electrical breaker to the heater, then close the cold-water inlet valve to prevent contaminated supply entering the tank. Open a hot tap elsewhere in the house to let air in, then draw from the drain valve at the base. Expect sediment in the first gallon or two. Do not restore gas or power until the tank is refilled — an element or burner fired into an empty tank will destroy it.
The plumbing itself. The pipes hold several gallons. Open the highest tap in the house to admit air, then drain from the lowest tap.
Toilet tanks. The tank — not the bowl — holds clean supply water, roughly 1.6 to 5 gallons (6–19 L) depending on age. Usable only if no in-tank cleaner, dye tablet or drop-in "blue" product has ever been used. Treat it before drinking.
Ice. Whatever is in the maker bin and trays. Also useful for keeping the fridge cold — see our backup power guide for how long a closed fridge holds.
Canned goods. The liquid in canned vegetables and fruit is drinkable and carries some calories and electrolytes. It is part of why a rotating deep pantry is worth more than a bucket kit.

Do not drink from waterbeds (chemically treated), radiators, boilers, hot tubs, or swimming pools. Pool water contains stabilisers and algaecides that are not intended for ingestion and are not removed by boiling — but it is excellent for flushing toilets and washing, and a full pool is a large sanitation reserve.

One timing point matters more than any of the above: do this early. If the utility loses pressure, contaminated groundwater can enter the distribution system, and whatever is in your pipes at that moment is no longer clean. Close the main as soon as a boil advisory or pressure loss is announced, and your house becomes a sealed reservoir.

Boiling: the default treatment, and the only one that handles everything biological

If you are unsure what to do with doubtful water and you have heat, boil it. Boiling inactivates bacteria, viruses and protozoa — including Cryptosporidium, which chlorine does not reliably kill. No other field method covers all three categories as completely.

The procedure, per CDC Emergency Preparedness and the EPA's emergency disinfection guidance:

1. Pre-filter if the water is cloudy. Let sediment settle, then pour the clear water off the top through a clean cloth or a paper coffee filter. Turbidity shields organisms and wastes fuel. 2. Bring to a rolling boil and hold it for 1 minute. 3. Above 6,500 ft (2,000 m), hold the rolling boil for 3 minutes. Water boils at a lower temperature as pressure drops, so the extra time compensates. 4. Let it cool naturally. Do not add ice to speed it up — you will reintroduce whatever the ice was made from. 5. Store it in a clean, covered container.

A rolling boil means continuous large bubbles breaking the surface, not the first small bubbles clinging to the bottom of the pot. When in doubt, look at the surface, not the base.

Boiled water tastes flat because the dissolved air has been driven off. Pour it back and forth between two clean containers a few times to re-aerate it, or add a very small pinch of salt per quart. This matters: people who dislike the taste of their treated water drink less of it.

The constraint is fuel, not knowledge. Boiling 56 gallons (212 L) over two weeks is a real energy budget. Confirm you have a heat source that works indoors safely, or outdoors in weather — a camp stove with spare canisters, or the ability to build and hold a fire in bad conditions, which is its own skill set and is covered in fire in the rain. Never run a charcoal grill, camp stove or generator inside a home, garage or tent. Carbon monoxide from combustion appliances used indoors kills people during outages every year.

Bleach disinfection: exact ratios, and the limits of chlorine

When you cannot boil, unscented household bleach is the standard chemical fallback. The EPA's emergency disinfection page is the authoritative source; these are its figures.

Before dosing: if the water is cloudy, let it settle and filter it through a clean cloth or coffee filter. Chlorine is consumed by organic material, so dirty water eats your dose before it reaches the pathogens.

Dosing with unscented household bleach (5–9% sodium hypochlorite):

1 quart / 1 litre: 2 drops of 6% bleach, or 2 drops of 8.25%
1 gallon (3.8 L): 8 drops of 6%, or 6 drops of 8.25%
2 gallons (7.6 L): 16 drops (1/4 tsp) of 6%, or 12 drops (1/8 tsp) of 8.25%
4 gallons (15 L): 1/3 tsp of 6%, or 1/4 tsp of 8.25%
8 gallons (30 L): 2/3 tsp of 6%, or 1/2 tsp of 8.25%

Double the dose if the water is cloudy, coloured, or very cold. Stir, then let it stand 30 minutes. It should have a faint chlorine smell afterwards. If it does not, repeat the dose and wait another 15 minutes before use. Read the concentration off your own bottle and check it against the EPA table rather than working from memory — label concentrations change.

What will not work:

Scented, colour-safe, "splash-less" or thickened bleaches. They contain surfactants and additives not intended for ingestion. Only plain, unscented sodium hypochlorite.
Old bleach. Sodium hypochlorite degrades, faster when warm. A jug that has spent two summers in a hot garage may be well below its labelled strength. Replace bleach annually and store it cool. This is the most common silent failure in a water kit.
**Bleach against Cryptosporidium.** Chlorine does not reliably inactivate it, and is less effective against Giardia than against bacteria. If protozoa are a plausible risk — surface water, livestock upstream, flooding — boil or use a filter rated for cyst removal.

Check this now, not later. Go to your supplies and read the bleach label. Does it state a sodium hypochlorite percentage? Is it unscented and plain? Is there a date code within the last year? Do you own a dropper, or a 1/8 teaspoon measure? If any answer is no, you do not have a working chlorine option, whatever the shelf suggests.

Filters and purifiers: what each actually removes

"Filter" and "purifier" are not synonyms, and the difference is the difference between removing bacteria and removing viruses. Pore size decides most of it.

Hollow-fibre membrane filters (0.1–0.2 micron). The common squeeze and gravity filters. Remove bacteria and protozoa, including Cryptosporidium and Giardia. Do not remove viruses — viruses are smaller than the pores. They also fail hard when frozen: ice ruptures the fibres and the filter passes water while no longer filtering, with no visible sign. Never let a used filter freeze.
Ceramic filters. Similar performance envelope, cleanable by scrubbing the element, heavier and breakable.
Filters certified to NSF/ANSI 53 or 58 for cyst reduction, or stating an absolute 1-micron rating, are the specification to look for if Cryptosporidium is your concern. "Nominal" 1 micron is not the same claim as "absolute."
Purifiers. Devices that claim virus removal do it with an additional mechanism — a chemical element, electrostatic media, or UV. If viruses are a plausible risk, which they are wherever human sewage may be involved, a filter alone is not enough. Filter first, then chemically treat the filtered water, or boil.
Activated carbon. Improves taste and odour and reduces some organic chemicals. It is not a disinfectant. Carbon alone does not make unsafe water safe.
Reverse osmosis and distillation. The only common household methods that address dissolved salts and many chemical contaminants. Slow, and distillation is fuel-hungry, but distillation will produce drinkable water from seawater or brackish water when nothing else will.

What none of them fix. Boiling, chlorine and standard filters do not remove fuel, solvents, pesticides, industrial chemicals, or heavy metals. Boiling makes chemical contamination worse by evaporating water and concentrating what remains. Flood water routinely carries sewage, fuel and agricultural chemicals at once. If you suspect chemical contamination, the answer is not a treatment method — it is a different water source.

Our approach to evaluating this kind of gear, including what we will and will not claim, is set out in how we test.

The drill: a 24-hour valve-off test with a pass condition

A stack of jugs is a hypothesis. This drill tests it. Pick an ordinary weekday — a Saturday with nothing planned is not a representative sample.

Setup

1. Locate your main water shutoff valve. Time yourself finding it. 2. Confirm you own whatever tool it needs. Many need nothing; some need a meter key. 3. Close the main. Do not run this drill if your home has a water-fed fire sprinkler system on the same supply, or if anyone in the household depends on water for medical equipment. 4. Live for 24 hours on stored water only. Cook, wash, drink, clean as normal. 5. Measure everything. Mark jug levels with tape, or count bottles. Write the number down.

Pass conditions — all three must hold

You located and closed the main in under 5 minutes, with tools you already own.
You went the full 24 hours without reopening it.
Your 24-hour total × 14 is less than or equal to what you actually have stored.

That third condition is the one that fails. A household of four that draws 6 gallons in a day is on a 84-gallon two-week trajectory, not 56. Either your consumption comes down — paper plates, dry shampoo, hand sanitiser instead of washing, a bucket-flush routine — or your storage goes up. Both are valid answers. Guessing is not.

Log three things afterwards: total gallons drawn, what you went without, and what broke. Then repeat in six months, when you rotate the water. Two data points from your own household beat any published average, and this is exactly the kind of check-with-a-standard we build every guide around — see start here for the rest of the sequence.

Common mistakes and failure modes

In rough order of how often they turn a manageable outage into a bad one:

Stopping at three days. Three days was never the recommendation for home storage; it is the minimum. Ready.gov's home target is two weeks. Most people who think they are prepared have three days.
Ignoring the sanitation half. They store drinking water, then use it to flush a toilet at 1.6 gallons (6 L) a go and burn a week of supply in an afternoon. Fill the bathtub, use pool or rain water, and keep the stored supply for mouths only.
Bleach that no longer works. Degraded, scented, or splash-less. The bottle is present, the capability is not.
Milk jugs. They seep, split at the seams, and cannot be sanitised. They will also fail quietly, under the bed, months before you look.
Everything in one place. One stack, in the room that floods or the garage that bakes. Split it.
No way to move it. A full 5-gallon jug is 43 lb (19.5 kg); a 55-gallon drum is 459 lb (208 kg) and has no drain fitting you can reach with a cup. If you cannot lift it or pump it, you do not have it. Buy the siphon pump at the same time as the drum.
A filter used against the wrong threat. A hollow-fibre filter on sewage-contaminated flood water passes viruses. A frozen filter passes everything.
No grab-and-go portion. All 56 gallons are in the basement and you have 10 minutes to evacuate. Keep a portable share with your 72-hour kit.
Assuming the tap is fine once pressure returns. Restored pressure is not a safety declaration. Wait for your utility to lift the advisory.
Forgetting the pets. They are household members with a daily water requirement, and improvising for them mid-event costs you water you had allocated elsewhere.
Never testing any of it. The drill above takes one day. It is the difference between a plan and a purchase.

Limits of this guide, and what to read next

Some of this is jurisdiction-dependent or medically specific, and we would rather say so than pretend otherwise.

Boil-water advisories are issued locally. Your utility's instruction supersedes anything on this page. Watch for alerts through the National Weather Service and your local emergency management channel.
Rainwater harvesting is regulated differently by state. Collection volumes and permitted uses vary. Check your own state's rules before building a system around a barrel.
Private wells have their own testing and post-flood disinfection procedures, which are not covered here and which your county health department publishes.
Medical situations — dialysis, immunosuppression, infant feeding, sodium-restricted diets — are clinical questions. Nothing here is medical advice; see the disclaimer.
Food safety after an outage is a separate arithmetic problem with its own temperature thresholds and time windows. FoodSafety.gov covers refrigerated and frozen food, and the National Center for Home Food Preservation covers preservation done properly.

Where the evidence here is thin, it is thin in one direction: published guidance gives you a defensible baseline, but it cannot tell you what your household consumes. That is what the drill is for.

Next, in the order we would tackle them: emergency food storage and the 30-day pantry, which shares shelf space and rotation discipline with this one; the rest of water and food storage; and backup power for a home outage, because the freezer and the well pump are both on the same list of things that stop when the grid does.