Pick the item. Pick the household. Pick the duration. Get the number.
Every household preparedness question that starts with "how much" ends in three variables. The answer is below — with the math, a worked example, and the situations that move the number up.
Twenty-four calculators built from the same 1-gallon-per-person-per-day and 2,000-calorie-per-person-per-day household-preparedness math.
How much water by household and duration
Drinking + cooking water by household size and duration.
| Household | 72 hours | 2 weeks | 3 months |
|---|---|---|---|
| 1 person | 3 gallons → | 14 gallons → | 90 gallons → |
| 2 people | 6 gallons → | 28 gallons → | 180 gallons → |
| 4 people (family) | 12 gallons → | 56 gallons → | 360 gallons → |
| 6 people (family) | 18 gallons → | 84 gallons → | 540 gallons → |
How much food by household and duration
Shelf-stable calories by household size and duration.
| Household | 72 hours | 2 weeks | 3 months |
|---|---|---|---|
| 1 person | 6,000 calories → | 28,000 calories → | 180,000 calories → |
| 2 people | 12,000 calories → | 56,000 calories → | 360,000 calories → |
| 4 people (family) | 24,000 calories → | 112,000 calories → | 720,000 calories → |
| 6 people (family) | 36,000 calories → | 168,000 calories → | 1,080,000 calories → |
One gallon, two thousand calories, multiplied out.
Water: 1 gallon per person per day for drinking and cooking, with another 0.5 gallon per person per day for hygiene if you want a comfortable posture. This is the FEMA / Ready.gov floor — not a high mark.
Food: 2,000 calories per person per day of shelf-stable food. Real numbers vary by age, body size, activity, and weather; the 2,000-calorie baseline is the sedentary-adult maintenance line. Add 20–30% for cold weather, hard work, or larger bodies.
Each calculator page above shows the math, walks a worked example, lists the situations that move the number up, and links to the related calculators across items, household sizes, and durations.
If you haven't yet, the Start Here assessment sizes the whole household to a Level — and the Level tells you which row of calculators is yours.