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Methodology · Official references · Important limitations

Water Requirements

The calculator uses the FEMA Ready.gov standard water recommendation as its baseline:

Water per person = 1 gallon (3.785 liters) per day
Water per pet    = 0.5 gallons (1.89 liters) per day

Total water (gallons) = (persons × 1.0 + pets × 0.5) × days

FEMA notes that this covers drinking and basic sanitation. Additional water may be needed for cooking, hygiene beyond basics, medical conditions, hot/dry climates, or pregnant and nursing individuals. The agency recommends storing at least a two-week supply for extended emergencies.

Caloric Requirements

Daily caloric needs are sourced from the USDA Dietary Guidelines for Americans, 2020–2025, Table A2-1 (Estimated Calorie Needs per Day by Age, Sex, and Physical Activity Level). The calculator uses three activity tiers:

Group	Sedentary	Moderate	Active	Notes
Adult Male	2,400 kcal	2,600 kcal	2,800 kcal	Ages 19–50 average
Adult Female	2,000 kcal	2,200 kcal	2,400 kcal	Ages 19–50 average
Child (under 12)	1,400 kcal	1,600 kcal	1,800 kcal	Mixed age average, 4–11
Pet (average)	~750 kcal/day			Average medium dog/cat

Activity Level Definitions (USDA):

• Sedentary: Only light physical activity associated with typical day-to-day life.
• Moderate: Physical activity equivalent to walking about 1.5–3 miles per day at 3–4 mph, in addition to light daily activity.
• Active: Physical activity equivalent to walking more than 3 miles per day, or significant manual labor.

Total calories = (males × male_kcal + females × female_kcal
                 + children × child_kcal + pets × 750) × days

Food Category Breakdowns

The food category weights are derived from USDA MyPlate daily serving recommendations, converted to approximate storage weights for planning purposes. An "adult equivalent" multiplier is applied:

Adult equivalent = adults + (children × 0.65)
  (Children represent ~65% of adult food needs by weight)

Category	Daily Basis (per adult)	Storage Approximation	Source
Grains & Starches	6 oz-equivalent/day	~1 lb = 16 oz dry grain	USDA MyPlate (2020)
Proteins	5.5 oz-equivalent/day	~0.85 lbs per standard can	USDA MyPlate (2020)
Fruits & Vegetables	4.5 cups/day combined	~1.5 cups per standard 15oz can	USDA MyPlate (2020)
Fats & Oils	6 tablespoons/day	1 oz ≈ 2 tablespoons oil	USDA Dietary Guidelines
Dairy / Supplements	3 cups/day	1 lb powdered milk ≈ 14 cups reconstituted	USDA MyPlate (2020)

These are planning approximations. Caloric density, serving sizes, and actual product weights vary by brand and product. Use these figures as a starting point and adjust based on the specific items you stock.

Storage Space & Budget Estimates

The storage volume estimate uses a rough industry convention of approximately 30 lbs of dry/canned food per cubic foot of storage space. This varies considerably by container type and product density.

Budget estimates use a range of $4.50–$9.00 per person per day, reflecting the difference between buying basic bulk staples (rice, beans, oats) versus a mixed supply including freeze-dried meals and more variety. Actual costs depend heavily on your local market, bulk purchasing, and brand choices.

Official Sources & Further Reading

Source	Relevance	Link
FEMA Ready.gov — Water	1 gal/person/day water storage standard	ready.gov/water
FEMA Ready.gov — Food	Emergency food supply guidance	ready.gov/food
USDA Dietary Guidelines 2020–2025	Caloric needs by age, sex, activity	dietaryguidelines.gov
USDA MyPlate	Daily food group serving recommendations	myplate.gov
American Red Cross	Emergency supply list and preparedness guidance	redcross.org
CDC Emergency Preparedness	Food and water safety during emergencies	cdc.gov/disasters
Utah State University Extension — Food Storage	Detailed household food storage quantity guides	extension.usu.edu

Known Limitations

• Age ranges: The calculator uses average caloric values. Needs differ for infants, teenagers, adults over 65, and pregnant or nursing individuals.
• Medical conditions: Diabetes, kidney disease, food allergies, and many other conditions require individualized dietary planning not captured by general averages.
• Climate and exertion: Extreme heat, cold, or physical labor in a survival scenario may significantly increase actual caloric and water needs beyond USDA averages.
• Pet variability: The 750 kcal/day average is suitable for a medium-sized dog or cat. Large dogs, working dogs, or multiple species may require very different amounts.
• Food density and waste: Actual caloric content of stored food depends on specific products. Some waste (spoilage, preparation loss) is inevitable and not modeled.
• Nutritional completeness: Caloric sufficiency does not equal nutritional completeness. Micronutrient needs (vitamins, minerals) should be supplemented, especially in long-duration storage scenarios.