How Much Water Should You Store Per Person? A Household Calculator

Quick answer: plan on at least one gallon of water per person per day, the figure used by Ready.gov and the American Red Cross. Keep a three-day supply in a go-bag or evacuation kit and aim for a two-week supply at home. Add more for hot weather, pregnancy, nursing, illness, young children and pets, and remember that the gallon covers drinking and basic hygiene, not flushing or laundry.

Most emergency checklists give the same short answer: one gallon per person per day. That figure is a good start, but a number on a list does not tell you how many jugs to buy for your own home, how long the supply should last, or who in the family needs extra.

This guide turns the official guidance into a worksheet. It explains where the gallon figure comes from, what it is meant to cover, how to adjust it for climate and health, and how to add up a total for a whole household. For the bigger picture on containers, treatment and filters, start with our emergency water guide, which is the hub for every water article on this site.

Where the One-Gallon Rule Comes From

Federal and relief agencies agree on the baseline. Ready.gov, the preparedness site run by FEMA, recommends storing at least one gallon of water per person per day for drinking and sanitation. The American Red Cross uses the same daily figure in its survival kit list.

Ready.gov also explains the reasoning. A normally active person needs about three-quarters of a gallon of fluid a day from water and other drinks. The rest of the gallon covers food preparation and basic hygiene, such as brushing teeth and washing hands. Individual needs vary with age, health, physical condition, activity, diet and climate, which is why the gallon is called a minimum and not a target.

Two durations show up in the guidance. The Red Cross suggests a three-day supply for evacuation and a two-week supply for home. Three days is the classic 72-hour kit standard, built around the idea that help may take that long to arrive after a disaster. Two weeks reflects longer disruptions, such as a damaged water main, a hurricane that knocks out treatment plants, or a boil-water notice that drags on.

Ready.gov adds a practical point that is easy to miss: if storing two weeks of water is not possible, store as much as space allows. A partial supply still buys time.

What One Gallon Covers and What It Does Not

A gallon a day sounds generous until you look at how a household actually uses water. Under normal conditions, a single shower or a load of laundry can use far more than a gallon. The emergency figure assumes a very different routine.

The gallon is meant for:

• Drinking water and other fluids
• Mixing powdered drinks or rehydrating food
• Brushing teeth and basic handwashing
• A quick sponge wash

It is not meant for:

• Flushing toilets
• Washing dishes the usual way
• Laundry
• Showers or baths
• Cleaning floors and surfaces after a flood

Toilets are the big gap. Toilets sold in the United States since the 1990s are limited by federal standards to 1.6 gallons per flush, and many newer models use less, but even an efficient toilet would eat a person’s whole daily allowance in one flush. Many families plan a separate supply of non-drinking water for flushing, such as a filled bathtub or rain barrel, and keep drinking water for drinking.

Pets also fall outside the gallon. Ready.gov’s pet guidance says to keep several days of water for each animal in your kit, so count them separately.

Who Needs More Than a Gallon

Ready.gov names several groups that may need more water than the baseline. Nursing mothers, children and people who are sick are on that list. A medical emergency can also raise the need, for example when someone is running a fever or has diarrhea and needs to replace lost fluid.

Hot weather matters most. Ready.gov notes that in very hot temperatures, water needs can double. That is a real concern for summer power outages, since an outage often means no air conditioning just when the body needs the most fluid. The National Weather Service heat safety pages also advise drinking plenty of fluids during heat waves and staying in the coolest place available.

Physical work raises the number too. Cleanup after a storm involves lifting, hauling and sweating, often in heat. Anyone doing that kind of work will drink more than the planning figure.

A simple adjustment table

Treat these as planning multipliers, not medical advice:

• Average adult in mild weather: 1 gallon per day
• Adult in hot weather or doing heavy cleanup: plan for 2 gallons per day, since Ready.gov says needs can double in very hot conditions
• Pregnant or nursing adult: add a margin and ask a doctor or midwife how much fluid is right
• Person who is ill: add a margin, and follow any instructions from a health care provider
• Infant on powdered formula: the formula needs safe water, so store water for mixing based on the label and the pediatrician’s guidance, or keep ready-to-feed formula, which needs no added water

People with medical conditions that affect fluid intake, such as kidney disease or heart failure, should ask their care team before planning. Some need to limit fluids rather than increase them.

Build Your Household Worksheet

Here is a step-by-step way to get to a total. Grab a notebook or open a spreadsheet.

1. List each person in the household and their base need, starting at 1 gallon per day.
2. Adjust each person for heat, pregnancy, nursing, illness or heavy work using the table above.
3. Add each pet’s daily water need, based on your veterinarian’s advice.
4. Add up the daily total for the household.
5. Multiply by 3 for the evacuation kit and by 14 for home storage.
6. Round up to the nearest container size you plan to buy.

Three worked examples

A single adult in a mild climate needs 3 gallons for a three-day kit and 14 gallons for two weeks at home.

A couple with two school-age children starts at 4 gallons a day. Three days comes to 12 gallons, while two weeks is 56 gallons. Planning for a summer outage in a hot region, where needs may double, pushes the two-week figure toward 112 gallons, so many families in hot climates choose a middle target and back it up with a way to treat more water.

A retired couple with a dog starts at 2 gallons a day for the people plus whatever the veterinarian recommends for the dog. If one person has a condition that calls for extra fluid, add that margin before multiplying.

These numbers are often bigger than people expect. That is normal, and it is a reason to build the supply in stages instead of buying it all at once.

Turn the Total Into Containers

Gallons are easy to count once you know your container sizes. A few common sizes:

• A case of 24 half-liter bottles holds about 3.2 gallons
• A standard store jug holds 1 gallon
• Many stackable storage jugs hold 3 to 7 gallons
• Food-grade drums commonly hold 15, 30 or 55 gallons

Weight is the other thing to plan for. Water weighs about 8.3 pounds per gallon. A full 5-gallon jug weighs more than 40 pounds, and a full 55-gallon drum weighs well over 400 pounds, which rules it out for many upper-floor apartments and makes it impossible to move once filled.

For apartment dwellers, our guide to storing emergency water in a small apartment covers space-saving containers, weight and lease issues in detail.

When choosing containers, Ready.gov recommends buying commercially bottled water or using food-grade containers. The FEMA and Red Cross guide on food and water in an emergency advises against reusing milk or fruit juice jugs, because the proteins and sugars left behind are hard to remove and can feed bacteria. Those thin jugs also tend to break down and leak over time.

Build the Supply in Stages

A two-week supply for a family can feel out of reach. Breaking it into stages makes it manageable and spreads the cost.

Stage 1: three days

Start with the three-day total for everyone in the household. A few cases of bottled water often cover it. Put part of this supply in or next to your go-bag so it travels with you in an evacuation, and keep the rest at home.

Stage 2: one week

Add enough to reach seven days. Stackable jugs make sense at this stage because they hold more in less floor space than bottles. Store them in cool, dark places spread around the home.

Stage 3: two weeks

Fill the gap to fourteen days. Larger containers can help if you have the space and a ground floor or garage. Apartment dwellers can stretch their supply with water that is already in the home. Our article on using your water heater and pipes as emergency water explains how to draw on the tens of gallons sitting in a typical water heater tank.

Stage 4: a backup plan

Even a full two-week supply can run out. A treatment method, such as unscented household bleach used according to label directions, a filter, or a way to boil water, lets you turn other sources into drinking water. Pair the stored supply with at least one way to treat more.

Using the Supply Wisely During an Emergency

Storing water is half the job. Using it well is the other half.

Ready.gov gives clear advice here: never ration drinking water unless authorities tell you to. Drink the amount you need today and try to find more for tomorrow. Cutting back on water to make the supply last can lead to dehydration, which is far more dangerous than running short of stored jugs. The same guidance suggests reducing activity and staying cool to lower how much water the body needs.

A few habits help stretch the non-drinking share:

• Use hand sanitizer for routine hand cleaning, and save water for times when hands are visibly dirty
• Wash dishes in a basin rather than under running water, or use paper plates for a few days
• Keep a separate bucket of non-drinking water for flushing
• Open the oldest containers first and keep track of how much is left

Pay attention to local news. If the outage is tied to a water main break or a contamination problem, the water utility will usually issue a notice. Our guide to boil water advisories explains what those notices mean and when the tap is safe again.

Check and Refresh the Plan

A supply that made sense last year may not fit this year. Households change. A new baby, an older relative moving in, a new pet or a move to a hotter climate all change the math.

Set a reminder once or twice a year to review the worksheet. Many people pair it with daylight saving time changes in spring and fall, along with testing smoke alarms. At the same time, check expiration dates on bottled water and refresh any water you bottled yourself. Ready.gov suggests replacing water stored in your own containers every six months.

Review where the supply is stored as well. Water kept in a hot garage or a sunny corner may not stay as fresh as water in a cool closet. If a container is leaking or cloudy, replace it.

Frequently Asked Questions

?? Is one gallon per person per day really enough?

It is the minimum used by Ready.gov and the American Red Cross for drinking and basic hygiene. Many people need more, especially in hot weather, during illness, while pregnant or nursing, or when doing physical work, so treat the gallon as a floor.

?? How much water should a family of four store?

At one gallon per person per day, a family of four needs 12 gallons for three days and 56 gallons for two weeks. Add more for hot climates, infants, pets and anyone with extra needs.

?? Does the gallon include water for flushing the toilet?

No. The planning figure covers drinking and basic sanitation. A single flush can use 1.6 gallons or more, so plan a separate supply of non-drinking water for flushing, such as a filled bathtub.

?? How much water does a pet need in an emergency?

Ready.gov recommends keeping several days of water for each pet in your kit. The right amount depends on the animal’s size, diet and health, so ask your veterinarian for a daily figure and add it to your total.

?? Should I store water for three days or two weeks?

Both. The American Red Cross suggests a three-day supply for evacuation and a two-week supply at home. Start with three days and build toward two weeks in stages.

?? Is it safe to drink less to make water last longer?

Ready.gov advises against rationing drinking water unless authorities tell you to. Drink what you need today, look for more for tomorrow, and reduce activity and stay cool to lower how much your body needs.

Sources: Ready.gov (Water; Build a Kit; Pets and Animals), FEMA and American Red Cross, Food and Water in an Emergency, American Red Cross Survival Kit Supplies, National Weather Service heat safety guidance. This article is general preparedness information, not medical advice. People with health conditions should ask a health care provider about their fluid needs.