How the water storage calculator works
For emergencies, power outages, or off grid trips, it helps to know how much water to keep on hand. This tool uses the common one gallon per person per day guideline, adds extra for hot conditions and pets, and multiplies by the number of days. It returns the total in gallons and liters, a per day figure, and how many standard containers that works out to.
How much water per person
Emergency guidance commonly recommends storing at least one gallon, about 3.8 liters, per person per day, with roughly half for drinking and half for cooking and basic hygiene. A three day supply is a sensible minimum, and two weeks is better if you have the space. Children, nursing parents, and anyone unwell may need more.
Pets, heat, and extra needs
Hot weather, high altitude, and physical activity raise how much people drink, so the conditions option bumps the figure up. Pets need water too; this tool adds about half a gallon a day per cat or dog, though large dogs need more. If you rely on water for medical equipment or a garden, add that on top.
Storing and rotating water safely
Use food grade containers made for water, keep them sealed, cool, and out of direct sunlight, and away from fuels or chemicals whose vapors can permeate plastic. Commercially bottled water keeps well; label home filled containers with the date and rotate them about every six months. If you ever need to treat questionable water, follow official guidance on boiling or disinfection.
Frequently asked questions
How much water should I store per person? At least one gallon per person per day, with a three day minimum and two weeks preferred.
How much for a family of four for three days? About 12 gallons, roughly 45 liters, at the standard rate.
How often should I rotate stored water? Commercially bottled water lasts well; rotate home filled containers about every six months.
Related calculators: Water Intake, Party Beverage, Coffee for a Crowd.