How much water you need for 3 days
Published
Be Ready says 3 litres per person per day, for drinking, for 3 days. For 1 adult, that's 9 litres for 3 days: 2 × 5-litre bottles.
How it works out for a family
For 2 adults and 2 children, that's 36 litres for 3 days: 8 × 5-litre bottles, or one 20-litre container plus 4 bottles. The calculator does this for your household, pets included.
Why it’s worth doing
In the government’s 2026 survey, 4% of adults had 3 days of bottled water at that rate, and 82% had less than a day. If you haven’t got round to it yet, you’re in good company.
Cooking and washing
Be Ready says you’d need more for cooking and washing, but doesn’t give a number. Our suggestion is 2 more litres per person per day. That’s our figure, not official advice. Tick “Include water for cooking and washing” in the calculator to add it.
Pets
Our suggestion is about 1 litre a day per dog (bigger dogs drink more) and 0.25 litres per cat or small pet. There’s more in pets: the 3-day list.
Free, cheap, and optional
- Free: refill clean bottles you already have with tap water. Our suggestion is to swap it at least every 6 months.
- Cheap: supermarket 5-litre bottles of still water. Own brand is fine. Check the best-before date and swap them before it.
- Optional: a pair of 20-litre containers, if you’d rather not have a stack of bottles. Our pick is the PowerChem 2 × 20-litre jerry cans (Ad).
Water is the one thing on the list you definitely won’t find a cheaper version of.
Where to keep it
Somewhere cool and dark, off the floor of the garage and away from chemicals like paint and cleaning products. A cupboard under the stairs is ideal. More on the water kit page, and what to do if your supply goes off on the water off page.