Emergency Water Needs Calculator
Estimate how much emergency water you need based on the number of people, the number of days, and daily use per person.
Water is the most critical resource in any emergency. Use this calculator to estimate your needs, then plan storage using practical guides like How Much Water to Store or container planning with 5-Gallon Jug Planning.
Calculate emergency water needs
Enter how many people you are planning for, how many days you want to cover, and how much water each person needs per day.
56 gallons
Based on 4 people for 14 days at 1 gallon per person per day.
How to use this calculator
Enter the number of people, the number of days, and the number of gallons each person needs per day. The calculator estimates total water in gallons and litres, plus a rough number of 5-gallon containers.
Tips for success
- FEMA minimum: at least 1 gallon per person per day.
- Store extra for hot climates, active individuals, or nursing mothers.
- Include cooking water and basic sanitation in your estimate.
- Rotate stored water every 6–12 months.
Practical note
The 1-gallon/person/day baseline assumes moderate temperatures plus minimal cooking. Hot climates, active work, nursing mothers, or extended sheltering without bathing alternatives can push real needs to 1.5–2 gallons per person per day. Round up when in doubt, and rotate stored water every 6–12 months to keep it potable.
Common mistakes
- Drinking only: planning for drinking and forgetting hygiene or cooking.
- One-size planning: using the same water amount for all climates and situations.
- Special needs: ignoring the needs of children, older adults, or pets.
- No rotation: assuming stored water will stay usable forever without rotation.
- Short estimates: not accounting for a longer outage than expected.
FAQ
How much emergency water should I store per person?
A common minimum planning number is 1 gallon per person per day, but many households choose to store more for comfort and flexibility.
Does this include water for pets?
No. This calculator only estimates water for people. Add extra for pets separately.
Should I store more than the minimum?
Usually yes. Hot weather, extra cleaning, cooking, and unexpected delays can all increase water use.
How many litres are in a US gallon?
One US gallon is about 3.785 litres.
How much water do I need for 7 days?
Using FEMA's 1-gallon-per-person-per-day baseline, a household of 4 needs 28 gallons for a 7-day supply. Hot climates, nursing mothers, or active work raise that to 1.5–2 gallons per person per day, which puts the same household between 42 and 56 gallons. Most preparedness experts recommend planning for 14 days of water rather than 7 once your household has space, since recovery from major outages routinely takes longer than the 72-hour FEMA minimum.
How long does stored water last?
Commercially bottled water can last several years if unopened and kept in a cool, dark place out of direct sunlight. Tap water stored in food-grade containers stays potable for about 6 months before it should be rotated. The water itself doesn't go bad but the container can leach plastic compounds over time and the water can pick up off flavors. Label every container with its fill date and rotate annually to be safe.
What about sanitation water?
The FEMA 1-gallon-per-person-per-day minimum covers drinking plus minimal sanitation (handwashing, basic hygiene, light cooking). For full sanitation needs (toilet flushing, bathing, laundry, dishes) you would need an additional 5 to 10 gallons per person per day, which is impractical to store long-term. The realistic plan is to store 1 to 2 gallons per person per day for drinking and critical hygiene, then plan to capture and treat rainwater or use a portable filter on local sources for everything else.
How much water do you need per person per day?
The widely recommended emergency minimum is 1 gallon (3.8 litres) per person per day. This covers drinking and basic sanitation.
However, many households plan for 2 to 3 gallons per day for better comfort, cooking, and hygiene.
How much water should you really store?
The commonly recommended minimum is 1 gallon per person per day, but many households choose to store more depending on comfort, climate, and usage.
- 1 gallon/day: survival minimum
- 2–3 gallons/day: more comfortable living
- Hot climates: significantly higher needs
- Families: storage scales quickly