Emergency Water Storage Calculator

What FEMA Actually Recommends

FEMA recommends 1 gallon per person per day as a minimum—half a gallon for drinking, half for sanitation and hygiene. In hot climates, during physical labor, or for nursing mothers, that baseline doubles to 2 gallons per person per day.

That one-gallon minimum is a survival floor, not a comfort target. It covers drinking and basic hygiene—brushing teeth, washing hands, sponge-bathing. It does not cover laundry, dish washing, or any cooking that requires boiling water. If your food storage plan includes rice, beans, or freeze-dried meals, you need cooking water on top of that gallon.

What Most People Get Wrong

• Forgetting pets. Dogs need roughly 1 oz of water per pound of body weight per day. A 60-pound dog drinks about half a gallon daily. Cats need 3.5–4.5 oz per 5 pounds. If you have livestock, multiply accordingly.
• Not planning for cooking water. Rehydrating a single freeze-dried meal takes 1–2 cups. Cooking a pot of rice takes 2–3 cups. Over a day, food preparation can add half a gallon per person to your water needs.
• Using non-food-grade containers. Milk jugs break down and leach chemicals within months. Repurposed chemical containers are never safe. Use only containers rated food-grade—HDPE plastic (#2) or food-safe stainless steel.
• Never rotating stored water. Commercially bottled water in sealed containers stays safe indefinitely, but taste degrades. Tap water stored at home should be rotated every 6–12 months, or treated with unscented household bleach (8 drops per gallon) at storage time.
• Storing everything in one location. A single 55-gallon drum is convenient but represents a single point of failure. Split your supply across multiple containers and locations when possible.

Storage Options at Every Scale

Your storage method depends on your space, budget, and how many days you're planning for.

• Commercial water bottles — easiest to start. Grab an extra case every grocery trip. No rotation needed. Good for 3–7 day supplies.
• 5-gallon jugs — stackable, portable, easy to rotate. Ideal for 1–2 week supplies. Available at most hardware stores for $8–$12 each.
• 55-gallon drums — the workhorse of long-term water storage. One drum covers a single person for almost two months. Use a bung wrench and siphon pump for access.
• WaterBOB bathtub bladders — fills your bathtub with 100 gallons of clean water when a storm warning gives you lead time. Not for long-term storage, but excellent for hurricanes and planned grid-down events.

For a deeper dive on storage methods, containers, and shelf life, check out our water storage guides in the Learning Center.

Purification as a Backup Plan

Stored water covers your baseline, but a backup purification method extends your supply indefinitely—as long as you have access to any water source. The three main options:

• Gravity filters (Berkey, ProOne) — no power needed, filters thousands of gallons before replacement. Best for home use.
• Purification tablets (Aquatabs, Katadyn Micropur) — lightweight, 5-year shelf life, ideal for bug-out bags. Treats 1 liter per tablet.
• UV treatment (SteriPEN) — kills 99.9% of bacteria and viruses in 90 seconds. Requires batteries or USB charging.

A gravity filter at home plus tablets in your go-bag covers both scenarios. Your stored water buys you time; purification buys you flexibility.