Emergency water calculator
Work out how much drinking water your household needs for 3, 7 or 14 days, including pets.
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 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 UK
The calculator can use this figure instead of SupKit's.
| Guidance | Drinking water a day |
|---|---|
| the United Kingdom | 3 L2 |
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. UK advice: store 3 litres of drinking water per person per day, with more needed for other uses such as washing.
How much water for a family of 4 for 7 days?
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.
- Be Ready Checklist (PDF, created 2026-10-15), UK Government (Cabinet Office) Be Ready campaign. Checked 28 October 2026. Contains public sector information licensed under the Open Government Licence v3.0.
We summarise official guidance in our own words. Always follow advice from your local authorities.
