How much emergency water does your household need?
Use a practical starting estimate of 1 U.S. gallon (3.8 liters) per person per day for drinking and basic sanitation. Change the numbers to fit your household, then make an actual storage plan.
Enter your household and planning period
3 people × 7 days × 1 U.S. gallon per person-day. A starting baseline, not a maximum or customized water-safety assessment.
Plan extra water for pets, infants, pregnancy, medical needs, high heat, physical activity, food preparation and accessibility. A 7-gallon container of water weighs about 58 pounds before the container itself—consider smaller containers you can safely lift.
Stored drinking water comes before filters
- Use safe bottled or properly stored drinking water first. Check container instructions and rotate water as needed.
- A filter straw is not the same as a purifier. Many backpacking microfilters remove some bacteria and parasites but not viruses.
- Radioactive or chemical contamination is different. Boiling or an ordinary hiking filter does not reliably remove dissolved chemicals or radioactive material; use sealed, verified safe water and follow health authorities.
Based on Ready.gov's emergency kit guidance and CDC emergency drinking-water information. This calculator makes no assessment of your local water quality.
Common emergency water questions
How much water should I store for four people?
Using the baseline of one U.S. gallon per person per day: 12 gallons for three days, 28 gallons for seven days, or 56 gallons for fourteen days. That's about 45, 106 or 212 liters respectively, before additional household needs. Ready.gov's emergency kit guidance is the starting reference.
Does the calculator include pets or special medical needs?
No. The baseline is for people only. Add separate quantities for pets, infant feeding, pregnancy, illness, medical equipment, high heat and other needs. These vary, and the calculator deliberately does not invent a universal allowance. If a medical device depends on water or electricity, consult its clinical and manufacturer guidance.
Is a water-filter straw enough for a two-week emergency?
Not by itself. Store verified safe drinking water first. Many outdoor microfilters handle certain bacteria and parasites but not viruses, fuel, toxic chemicals or radioactive contamination. A treatment method must match the known hazard and current public-health instructions. CDC emergency drinking-water advice.
How is the container number calculated?
The calculator subtracts your existing safe-water inventory from the human baseline, divides the remaining amount by seven gallons, and rounds up. The seven-gallon container is only an example; choose the size you can safely carry and store. Water weighs roughly 8.3 pounds per U.S. gallon, so seven gallons of water alone weigh about 58 pounds.
Reviewed November 4, 2026. Formulas use U.S. gallons and the exact conversion of 3.785411784 liters per gallon. This is general educational planning, not a real-time water-quality assessment or a substitute for local advisories.