Household size and days turned into a water store
Enter the household size, the number of days you are preparing for, the per-person daily use in gallons, and the size of the containers you will fill. The page returns the total water to store, the number of containers, the spare room left in the last one, a doubled figure for very hot weather, and whether the number of days meets the minimum in the guidance. The container count is rounded up once at the end.
Where the default figure comes from
The default of one gallon per person per day, covering drinking and sanitation together, is the figure in US Federal Emergency Management Agency guidance, which also sets a minimum of three days per person. That guidance notes that children, nursing mothers and sick people need more, and that very hot weather can double the amount needed, which is why the doubled figure is shown beside the base one. The per-person figure stays editable so you can substitute a local one. Current as of October 2026.
Limits and disclaimer
This page works out quantities only; storage life and disinfection are not covered. Follow the container's own labeling and the maker's instructions for how long water may be kept, and check announcements from your local water utility for outage notices and emergency supply points.
Frequently Asked Questions
It is the figure in US Federal Emergency Management Agency guidance, covering drinking and sanitation together. The field stays editable so a local figure can be used instead.
The same guidance sets a minimum of three days per person. The page shows whether the number of days you entered meets that minimum, and does not recommend a longer period of its own.
The guidance notes that very hot weather can double the amount needed, so the page shows the doubled total and the container count that goes with it alongside the base figure.