Water is the first thing you should store — and the easiest to under-plan. This calculator works out exactly how many gallons your household needs, broken down by drinking, cooking, and sanitation, so you don’t guess.
💧 Calculate Your Water Needs
Why Water Counts First
The rule of thumb is one gallon per person per day — but that’s a minimum, not a plan. It drops quickly in heat, with physical activity, and once you account for cooking, cleaning, and pets. Most people under-store by half.
FEMA recommends at least one gallon per person per day for three days as the absolute floor. For longer-term or off-grid planning, two gallons per person per day is a far more realistic target. This calculator uses your inputs to build a defensible number so you stop guessing.
For the practical side of actually storing it, see our guides on emergency water storage and the best water storage containers.
Water Use Breakdown
| Use | Per Person Per Day | Notes |
|---|---|---|
| Drinking | 0.5–1 gallon | More in heat or for active individuals |
| Cooking | 0.25–0.5 gallon | Higher if relying on dry goods that need hydration |
| Sanitation / hygiene | 0.5–1 gallon | Can be reduced in emergencies |
| Practical target | 1.5–2 gallons | 1 gallon is the floor; 2 is comfortable |