The calculator
Shelter-in-place uses 2 meals and 3 litres of water per person per day. On the move (heat, walking, debris) uses 3 meals and 4 litres. Two snacks count as one light meal. The runway is the minimum of food-days and water-days, floored. A leftover half-day is not a plan.
Group size
Activity
Meals on hand
Ready-to-eat counts. A big pot of stew = how many bowls?
Snacks
Two snacks ≈ one light meal in this estimate.
Water (litres)
What you can actually pour. Not the stream down the hill.
Runway
3DAYS
Food and water run out together. Unusual, and useful.
Meal-equivalents
15
People
2
Food days
3
Water days
3
Field estimate, not nutrition science. 2 snacks ≈ 1 light meal. Does not model children, illness, or 40 °C heat.
Water need: worked numbers
Water is usually the limiter. A family of four with 40 litres and a cupboard of cans will hit thirst before hunger if they stay active. Treat the number as a reason to fetch or purify water today, not as permission to wait until day six.
What this will not do
It does not read barcodes, model infants, or promise that 3 L is enough at 40 °C. The app can estimate a pantry from a typed list with on-device AI; this page is the same arithmetic without that model. Purification methods live on the water hub. Litres of dirty river do not count until they are drinkable.
Further in the library: titles only
5 titles · 413 articles in this cluster · full text in-app
- 01Water Storage and Purification for Emergencies: CERT-Recommended Methods
- 02Survival Food Priorities: When to Seek Food, Water, or Shelter First
- 03Building a Survival Kit: Level 1, 2, and 3 Essentials
- 04First Aid Kit Checklist for Disaster Preparedness: What Every Home Needs
- 05Hot Climate Survival Kit: Essential Gear for Extreme Heat
Titles only. Full text, regional variants, and tables are in the offline library. They are not published on this site.
Then get it on the phone
You’re reading this with a signal. The situation it describes is one where you won’t have one.