Emergency Supply Duration Calculator
Estimate how long your emergency supplies (food, water, medicine, fuel, etc.) will last given your stock, daily consumption rate, and the number of people depending on them.
Units per person per day (e.g. 2 liters/person/day for water)
Reserve this percentage of supply as an emergency buffer (not counted toward usable days)
Formulas Used
Buffer Quantity:
Buffer Qty = Total Quantity × (Buffer % ÷ 100)
Usable Quantity:
Usable Qty = Total Quantity − Buffer Qty
Total Daily Consumption:
Total Daily = Daily Per Person × Number of People
Duration (days):
Duration = Usable Qty ÷ Total Daily Consumption
Duration (weeks / months):
Weeks = Duration ÷ 7 | Months = Duration ÷ 30.4375
Target Coverage (%):
Coverage = (Total Quantity ÷ (Total Daily × Target Days)) × 100
Assumptions & References
- The minimum drinking water recommendation is 1 gallon (≈ 3.8 L) per person per day for drinking and sanitation — FEMA / Ready.gov.
- A 3-day supply is the minimum recommended by FEMA for short-term emergencies; 2 weeks is recommended for extended disruptions.
- The safety buffer represents a reserve that should only be used as a last resort; it is excluded from the primary duration calculation.
- Daily consumption figures are averages; actual needs may vary with age, health, climate, and activity level.
- One month is approximated as 30.4375 days (365.25 ÷ 12) for consistency.
- Food caloric needs: ~2,000–2,500 kcal/day per adult; adjust per-person quantities accordingly.
- References: FEMA Emergency Supply List, CDC Emergency Preparedness, Red Cross Disaster Preparedness Guide.