Emergency Water Storage Calculator and Planning Guide

Updated September 26, 2026

An emergency water calculator provides a planning baseline, not a guarantee that every need is covered. The CDC recommends storing at least one gallon per person per day for three days and trying to store a two-week supply when possible.

Basic household calculation

Gallons needed = number of people × number of days × 1 gallon.

Examples:

• 2 people for 3 days: 6 gallons;
• 4 people for 7 days: 28 gallons; and
• 4 people for 14 days: 56 gallons.

This baseline covers drinking, cooking, brushing teeth, and limited hygiene. It does not include normal showers, laundry, or toilet flushing.

When to increase the amount

The CDC emergency-water guidance recommends considering additional water for hot climates, pregnancy or nursing, illness, pets, and other household needs. Also plan extra water for:

• medications or medical equipment;
• powdered infant formula, when applicable;
• physically demanding work;
• evaporation, spills, and damaged containers; and
• longer restoration times for wells or rural systems.

Pets and animals

Use the animal’s normal daily consumption as the starting point and add reserve for heat and activity. Veterinarians or agricultural extension services can help estimate unusual livestock or medical needs.

Container planning

Unopened commercial bottled water is a reliable emergency option. For home-filled storage, use food-grade water containers, sanitize and fill them correctly, label the date, keep them away from fuels and chemicals, and replace the water on the recommended schedule. CDC advises replacing home-filled water every six months.

Multiple smaller containers are easier to move and reduce the chance that one leak destroys the entire reserve. Large drums use space efficiently but require a safe floor location and a clean pump or dispensing method.

Storage is not treatment

Keep stored potable water separate from water reserved for flushing or cleaning. Filters, disinfectants, and distillers have different capabilities; no single method addresses every contaminant. Water suspected of containing fuel, toxic chemicals, or radioactive material requires another safe source and public-health guidance.

Current planning resources

Compare available long-term emergency water, portable filtration, and whole-house treatment by their actual use case. The unavailable AquaViable AV-5 has been removed and is not used in the calculation.

Bottom line

Start with people × days × one gallon, then add household-specific needs and a practical reserve. Store water in several safe locations, inspect it regularly, and maintain a treatment and replenishment plan.