How Much Water Do You Need for 90 Days (and How to Store It)

Water is the first thing every preparedness plan should cover, and it's also where people most often guess. This guide walks through the math, the storage options, and a two-layer strategy that makes a 90-day goal realistic for a real household.

The Starting Number: One Gallon Per Person Per Day

Ready.gov recommends storing at least one gallon of water per person per day, for drinking and sanitation. It also notes that a normally active person needs about three-quarters of a gallon of fluid daily, and that needs vary with age, health, activity, diet, and climate:

• Children, nursing mothers, and people who are sick may need more.
• In very hot temperatures, water needs can double.
• A medical emergency might require additional water.

Don't forget pets. Ready.gov's kit checklist specifically includes extra water for your pet.

The 90-Day Math

At one gallon per person per day:

Treat these as minimums. If you live somewhere hot, have little ones, or want water for more than drinking and basic hygiene, plan for more.

Those numbers can feel big. That's why most families use two layers: a stored reserve they can rely on completely, plus a way to treat and filter additional water.

Layer 1: Stored Water You Can Count On

Ready.gov's first recommendation is simple: buy commercially bottled water and keep it sealed in its original container in a cool, dark place. If you fill your own containers, use food-grade containers, clean and sanitize them first, and replace that water every six months.

For a long-term reserve, packaging matters. Plastic bottles and jugs are convenient, but they're bulky and need rotating.

ReadyPantry pick: Ready Pantry 12 oz Emergency Water. Canned drinking water with a 50-year shelf life and zero plastic. It's purified through a multi-stage process that includes active charcoal filtration, reverse osmosis, and UV treatment. Each case holds 24 cans (about 2.25 gallons), and you can order by the case, or choose a 25-case (1/4 pallet, roughly 56 gallons), 50-case (1/2 pallet, roughly 112 gallons), or 100-case (full pallet, roughly 225 gallons) pack. Quarter, half, and full pallets ship by freight.

What does that look like in practice?

• A half pallet covers one person for about 90 days, or a couple for nearly two months, at the one-gallon guideline.
• A full pallet covers a couple for about 90 days with some to spare, or a family of four for about eight weeks.

Small 12 oz cans have a practical upside, too. You open only what you need, there's no half-used jug sitting open, and they stack neatly.

Storage tips for canned and bottled water

• Keep it cool, dry, and dark. A basement, interior closet, or climate-controlled garage space works well.
• Protect it from freezing. Water expands when it freezes and can split containers, so store it somewhere that stays above freezing.
• Keep it away from chemicals, fuels, and solvents, and check cans for dents or damage when you rotate your stock.
• Spread it out. If you can, store some water in more than one spot in your home.
• Label and log it. Note what you have and where, so you can track it at a glance.

Layer 2: Filtration and Treatment to Stretch Your Supply

Stored water is your dependable core. Filtration lets you go further, whether that's water from your tap, a rain barrel, or another source.

Know what each method does. The CDC's guidance on making water safe in an emergency explains:

• Boiling is the best way to kill germs. Bring clear water to a rolling boil for 1 minute, or 3 minutes above 6,500 feet.
• Chemical disinfection with unscented household bleach, used at the right dose, kills most germs, though it's less effective against some parasites.
• Portable filters vary. Pore size determines what they remove, and the CDC recommends adding a disinfectant after filtering to address viruses and bacteria.
• No method fixes fuel or toxic chemicals. If you suspect your water contains fuel or chemicals, use stored water and contact your health department.

That's exactly why stored water stays the foundation, and filtration is the extender.

ReadyPantry pick: Sentry Portable System. A carry-anywhere filter system with a handle, hanging hook, and plug-and-go hose fittings. Choose the Standard filter set for city or pre-treated water, or the Premium set, which Sentry designed for sources with higher biological and chemical contamination. Keep a spare set of Portable Replacement Filters on your shelf, since Sentry recommends changing filters every year.

ReadyPantry pick: Sentry Wellness System. An under-sink system for everyday drinking water at your kitchen tap, available as the 2-filter DualGuard or 3-filter TriGuard. Add Wellness System Replacement Filters so you're not waiting on shipping during a disruption.

ReadyPantry pick: BOXIO Wash Up Water Filter System. A compact, stackable filter system for camp-style water needs. BOXIO says it filters 99.99% of bacteria and microplastics.

Not sure which filter fits your home? Our Water Filter Chooser walks you through it in a few questions.

Don't Forget Water for Cleaning

Drinking water gets the attention, but over 90 days, hygiene and dishwashing add up. Ways to save your drinking reserve:

• Use filtered or treated water for washing dishes and hands.
• A gravity or pump sink like the BOXIO Wash XL Camping Sink gives you running water for handwashing and toothbrushing without pressure from the tap.
• A composting toilet such as the BOXIO Toilet Plus uses no water at all.

More on that in Sanitation and Hygiene When the Grid Is Down.

Smart Habits During an Outage

Ready.gov's water tips are worth remembering:

• Never ration drinking water unless authorities tell you to. Drink what you need today and look for more tomorrow.
• Drink water you know is safe first.
• Reduce how much water your body needs by staying cool and limiting heavy activity.
• Avoid relying on caffeinated drinks and alcohol in place of water.

Your Water Plan in Three Steps

1. Calculate: people × 90 days × 1 gallon, then add extra for pets and hot weather.
2. Store: build a sealed reserve, using canned water by the case or by the quarter, half, or full pallet for long-term storage. Quarter, half, and full pallets ship by freight.
3. Extend: add filtration and spare filters so your supply keeps going.

Ready to build your water plan? Explore Water & Purification, use the Water Filter Chooser, or see the full picture on our 90-Day Ready hub.

Sources: Ready.gov: Water; Ready.gov: Build a Kit; CDC: How to Make Water Safe in an Emergency.