How much water does a family of 4 need for 3 days?

The short answer

Twelve gallons. That is four people for three days at a gallon each per day, and it weighs about 100 pounds.

Gallons

100 lb

What it weighs

7-gallon jugs

This is the easy one, and it is the only water page where bottled wins

Twelve gallons is five cases of bottled water, or two seven-gallon jugs with a little spare. It fits on one shelf of a cupboard. Everywhere else on this site we argue against buying cases of bottled water, because at larger volumes it is expensive, bulky and fragile. At seventy-two hours that argument stops applying. You will drink the lot before storage life matters, the cases stack on a shelf nobody is using, and the barrier to actually doing it is almost zero. If three days is where you are starting, buy the cases this week and move on to food.

Seventy-two hours is a floor, not a target

Three days is the figure most official advice leads with, and it comes from how long it typically takes organised help to reach a large affected area. It is a reasonable minimum and it is not what most real outages look like. Hurricane Beryl left parts of Houston without power for more than a week in July 2024. Treat twelve gallons as the version you can finish this afternoon, then plan the fortnight at your own pace.

Where the three days actually goes

Roughly half of that gallon per person is drinking and cooking, and the rest is hands, faces, teeth and dishes. People consistently underestimate the second half, then find themselves rationing drinking water to wash with. If your mains supply is still running and only the power is out, this matters far less, because you can wash from the tap and your stored water is purely drinking. Those are two very different situations and it is worth knowing which one you are in.

Keep track of your 12 gallons as you actually buy them.

Provision Planner counts the water already in your house against the target on this page, and tells you how many days you really cover. Your household and gallon figure carry across, so there is nothing to type in twice.

See how many days you cover

The next questions, answered

Is bottled water good for 3 days of emergency supply?

Yes, and this is the one case where it is clearly the right call. Five cases covers a family of four for seventy-two hours, it stacks on a shelf, and you will drink it long before shelf life is a question.

Does a family of 4 need more than 3 days of water?

Most households should work towards two weeks, which is fifty-six gallons. Three days is a sensible starting point rather than a finishing one, because real outages routinely run longer than seventy-two hours.

Water is one part of it. See the full supply plan for this household, which covers the food alongside it.