Water Storage Calculator
Estimate how much drinking water to store for your household, or how long an existing supply will last. The calculator uses a common emergency-planning baseline of about one gallon of water per person per day.
Default is 1 gallon per person per day (about half for drinking, half for cooking and sanitation). Increase it for hot climates, physical exertion, illness, or nursing mothers.
For 4 people over 14 days at 1 gal/person/day.
Emergency-preparedness guidance commonly suggests storing at least a 3-day supply, and a two-week supply where space allows. These are planning estimates — your actual needs may be higher.
Approximate water-storage planning estimates based on a baseline of about one gallon per person per day. Actual needs vary with climate, activity, health, age, and whether the supply covers only drinking or also cooking and sanitation.
How much water should you store?
A widely used preparedness guideline is to store at least one gallon of water per person per day. Roughly half of that is for drinking, and the rest covers food preparation and basic hygiene. A common recommendation is to keep at least a three-day supply for evacuation and, where storage space allows, a two-week supply to stay at home.
For a household of four planning a two-week supply at one gallon per person per day, that works out to 4 × 14 = 56 gallons. The calculator lets you adjust the per-person rate, the number of people, the number of days, and an optional allowance for pets.
Factors that increase water needs
Several situations raise the amount you should store above the baseline. Hot climates and physical exertion can roughly double drinking-water needs. Children, nursing mothers, and people who are ill or pregnant generally need more. Pets add to the total — a rough planning figure is about one ounce of water per pound of body weight per day for dogs and cats, which you can convert and add as extra gallons per day. Medical needs and sanitation beyond the basics also add up.
Storing water safely
Use food-grade containers intended for water, keep them sealed and out of direct sunlight, and label them with the date. Commercially bottled water is the most reliable option; if you store tap water, replace it periodically. This calculator estimates quantity only — it does not address water treatment, purification, or rotation schedules, which are important parts of a complete plan.
Assumptions and limitations
The figures here are approximate planning estimates, not guaranteed requirements. They assume a steady per-person daily rate and do not account for leaks, evaporation, spillage, or contamination losses. The default of one gallon per person per day is a general baseline; your actual needs may be higher, especially in hot weather or for vulnerable household members. Use this as a starting point and adjust for your own situation.
Disclaimer: This calculator is for general planning only and does not constitute emergency, medical, or safety advice. For authoritative guidance on emergency water storage and treatment, consult official preparedness resources from your local emergency-management agency.
References and cross-checks
- Ready.gov — Water (one gallon per person per day for drinking and sanitation).
- CDC — How to Create and Store an Emergency Water Supply (at least 1 gallon per person per day for 3 days; try for 2 weeks if possible).
- American Red Cross — Survival Kit Supplies (3-day supply for evacuation, 2-week supply for home).
These official preparedness sources are provided as references for the one-gallon-per-person-per-day baseline and the 3-day / 2-week supply guidance. Actual requirements depend on climate, activity, health, and local conditions.