A gallon a day is a planning figure, not a rule
About one gallon per person per day, covering drinking and basic sanitation, is the number in general circulation for household water planning. It is a reasonable starting point and it is the default in the field above, but it is worth understanding what it is and is not. It is an average across ordinary adults in ordinary conditions. It is not a medical figure, it is not adjusted for heat or exertion, and the specific quantities published by emergency management bodies get revised and differ by region. That is why every quantity on this page is an input you can change rather than a constant baked into the arithmetic.
Three things push the real requirement up. Heat and physical work raise fluid needs substantially, which is what the uplift field is for. Cooking consumes water that never gets counted, because rehydrating dried food, boiling pasta and rinsing a pan all come out of the same store. And washing is the line item almost everyone omits at planning time and nobody omits in practice. Add cooking and washing at the modest defaults here and the household requirement is roughly 1.75 gallons per person per day, not one.
Water is heavy, and the weight is the actual constraint
A US gallon of water weighs 8.34 pounds. That single fact reshapes the whole problem, because it turns a shopping decision into a structural and mobility one.
| Quantity | Weight | What that means in practice |
|---|---|---|
| 1 gallon jug | 8.3 lb | Anybody can carry two. The unit that actually leaves the house |
| 5 gallon container | 42 lb | One awkward but manageable lift for most adults, over a short distance |
| 7 gallon container | 58 lb | A two-person lift for many people, and a poor choice for stairs |
| 55 gallon drum | 459 lb | Filled where it stands, emptied with a pump, and never moved again |
| A week for four people, all uses | Around 440 lb | More than a domestic shelf is designed for. Spread it out and keep it low |
Two consequences follow. If it is on a shelf, an upper floor or anything other than a slab, the load per square foot matters and the optional area field gives it to you. And if there is any chance you will need to leave, the storage cannot all be in drums, because a drum is a stay-put container. A split store, with the bulk in large containers and a day or two in things one person can pick up, is the arrangement that survives both scenarios.
Pets, and the part of the plan that gets forgotten
Pets drink, and their requirement scales with size and species in a way no single figure captures. The default here is half a gallon a day per animal, which is generous for a cat and thin for a large dog in summer, and it is an input for that reason. If an animal in the household has a condition that affects fluid intake, that question belongs with your vet and not with a table.
Beyond drinking, animals add water demand you would not think to count: rinsing bowls, cleaning up, and in hot weather cooling. If you have livestock or poultry rather than household pets, the numbers change by an order of magnitude and this page is the wrong tool.
Rotation, and treating water you are not sure about
Stored water does not stay stored indefinitely. Containers, temperature, light and what was in the container beforehand all matter, and commercially bottled water carries its own dating. The practical answer is a rotation schedule tied to something already on the calendar rather than a date you have to remember, which is the same hook the family emergency plan uses for the rest of the kit.
Treating water of uncertain quality is a genuinely technical subject with tested procedures, and the methods, ratios and contact times differ by the contamination you are dealing with. Those procedures are published by health authorities and by your own water utility, which is also the body that will tell you whether a boil notice is in effect for your area. Go to them for it. Nothing on this page is a substitute, and a calculator is the wrong place to learn a purification method.
Where this fits with the rest
Water is the heaviest thing in a household plan, and it interacts with everything else in it. Once you know the gallons, the emergency kit weight calculator tells you how much of it can realistically be carried and by whom. If the reason you are storing water is a power outage rather than a supply interruption, the power outage timeline shows what else in the house is on a clock. And if leaving is a possibility, the evacuation timing planner deals with the part where a loaded vehicle and a full house do not happen in the same fifteen minutes.
Questions people ask
How much water should I store per person?
The commonly cited planning figure is about a gallon per person per day covering drinking and basic sanitation, and this page starts there. It is a planning number that varies by region and gets revised, so treat it as an editable input rather than a rule. What it does not include is cooking and washing, which is why the default household total here comes out closer to 1.75 gallons per person per day. Set the days to whatever your own situation calls for: three days is a sensible floor for a household with nothing stored today, and two weeks is a common target for areas where supply interruptions run long.
How much does stored water weigh?
A US gallon weighs 8.34 pounds, so a five gallon container is about 42 pounds full and a 55 gallon drum is about 459 pounds. A week of all-uses water for four people lands somewhere around 440 pounds. That weight is the reason storage location matters: it belongs low, spread over more than one spot, and on something you have checked can take it if it is not sitting on a slab. The optional floor area field gives you the load per square foot directly.
What size containers are best?
It depends entirely on whether the water has to move. Large drums store the most per square foot and are the cheapest way to hold a lot, but at several hundred pounds they are filled in place and emptied with a pump, and they will not be going anywhere with you. Containers around five gallons are the largest most adults will carry any distance. One and two and a half gallon jugs are the only sizes that realistically leave in a hurry. Most households end up with a mix, and the split is worth deciding deliberately rather than by accident.
Can I just refill old drink bottles?
Container choice, cleaning and how long stored water keeps are questions with real answers, and they depend on what the container previously held and how it is stored. Your water utility and your local or national health authority publish guidance on containers and on rotation intervals, and that is where the answer should come from. What this page can tell you is the quantity, the weight and the count, which is the part that governs whether the plan is physically possible in the space you have.
Do I need separate water for washing and flushing?
Most households end up separating them, because the volumes are very different and the quality requirement is too. Water for flushing does not need to be drinkable, so rainwater, a filled bathtub or containers set aside for the purpose all serve, and keeping that demand off the drinking store is what stops the store draining in two days instead of seven. The washing figure in this calculator covers hands, dishes and teeth rather than flushing, which is a much larger number per use and is normally handled another way.