Shelter Supply Calculator
FEMA recommends a minimum 14-day supply of water, food, and critical medications for every member of your household — including pets. This calculator gives you exact quantities based on your specific situation, so you are not guessing when it matters most.
The calculations below are derived from the FEMA Emergency Supply Kit guidelines, the CDC Radiation Emergency resources, and the HHS Radiation Emergency Medical Management (REMM) protocols.
Your Household
Your Requirements
Total Water Needed
70 gallons
Drinking + sanitation combined
Why These Quantities?
Water: The Non-Negotiable
FEMA's recommendation of one gallon per person per day is not arbitrary — it is the minimum calculated threshold for drinking (approximately half a gallon) and basic hygiene (the other half). During a nuclear emergency, municipal water systems may be contaminated by radioactive fallout or physically destroyed. The 14-day window corresponds to the radiation decay timeline: after two weeks, fallout radiation has dropped to roughly 1% of its peak level, making it safer to access external water sources or receive official guidance on water safety.
For infants and young children, the calculation is lower because their body mass is smaller — but the quality requirements are higher. Bottled formula or pre-boiled water in sealed containers is essential for infants under 12 months, as their immune systems cannot tolerate even trace contamination.
Source: FEMA Ready.gov — Emergency Supply Kit: "Store at least one gallon of water per person per day for several days, for drinking and sanitation."
Calories: Survival Metabolism
The caloric requirements in this calculator are based on the Estimated Energy Requirements (EER) from the U.S. Department of Health and Human Services. In a shelter situation, physical activity is reduced, but psychological stress significantly increases metabolic demand. The moderate activity level (2,000 kcal/day for adults) accounts for this balance. Prioritize calorie-dense, shelf-stable foods: canned beans, rice, oats, peanut butter, and dried fruit provide the best calorie-to-weight ratio.
Potassium Iodide (KI): What It Does and Does Not Do
KI tablets protect only the thyroid gland from radioactive iodine-131 — one specific isotope released in nuclear explosions and reactor accidents. They work by saturating the thyroid with stable (non-radioactive) iodine, so it cannot absorb the radioactive version. KI does not protect against other types of radiation, and it does not protect any other organ. The dosage varies by age: adults (18–40) take 130mg, adolescents (3–17) take 65mg, infants take 32mg. KI should only be taken when directed by public health authorities, as improper use can cause thyroid damage.
Source: FDA — Potassium Iodide (KI): "KI (potassium iodide) is a salt of stable (not radioactive) iodine that can help block radioactive iodine from being absorbed by the thyroid gland, thus protecting this gland from radiation injury."
Shelter Space: Why 10 Square Feet Matters
The 10 square feet per person minimum is a psychological and physiological threshold. Below this density, confined groups experience significantly elevated stress responses, impaired decision-making, and increased conflict — all of which reduce survival probability. In practice, aim for 15–20 sq ft per person if possible. The most important factor is not total space, but the protection factor (PF) of the shelter — the ratio of radiation outside to radiation inside. A basement of a multi-story concrete building has a PF of 100–1,000, meaning it reduces radiation exposure by 100 to 1,000 times.
Sources: FEMA Ready.gov · CDC Radiation Emergencies · FDA Potassium Iodide · HHS/REMM
Medical Disclaimer
The calculations provided are for general educational purposes based on publicly available FEMA and CDC guidelines. They are not a substitute for personalized medical advice. KI dosage information is educational only — always follow instructions from public health authorities. Consult a medical professional for guidance specific to your health conditions. In an actual emergency, follow instructions from local emergency management agencies.