Emergency water calculator
Work out how much drinking water your household needs for 3, 7 or 14 days, including pets, in gallons and litres.
SupKit plans on 3 litres of drinking water per person per day, for up to 14 days of stored water.1 For 4 people for 7 days that's 22.2 gallons (84 L). Pets need their own water on top.
How it works
The calculator runs the same engine as the SupKit app: people at home, times the days you choose, times the drinking water per person, plus each pet's water by species and size.
| SupKit figure | Amount |
|---|---|
| Drinking water | 3 L per person per day |
| Extra for washing (suggested) | 2 L per person per day |
| Stored water planned for up to | 14 days |
Official guidance in the US
The calculator can use these figures instead of SupKit's.
Storing that much water
Bottled water is easiest to rotate: use it in everyday life before its date and replace it. If space is tight, store the first few days and add a water filter or purification tablets for the rest.
Questions
How much water do I need per person per day?
SupKit plans on 3 litres of drinking water per person per day. Ready.gov advises at least one gallon of water per person per day, for drinking and sanitation.
How much water for a family of 4 for 7 days?
22.2 gallons (84 L) of drinking water, at SupKit's 3 litres per person per day.
Sources
- SupKit planning rules (SupScore 2026.5), SupKit. SupKit's own planning data.
- Water, Ready.gov (US DHS / FEMA). Checked 28 October 2026.
- Kits (2 Weeks Ready), Washington Military Department, Emergency Management Division. Checked 28 October 2026.
We summarise official guidance in our own words. Always follow advice from your local authorities.
