Emergency water calculator
Enter who lives in your home and how long you want to be covered. We’ll work out how much drinking water to store, including your pets.
Your result
Affiliate disclosure: Some links on this site are affiliate links. If you buy through them we may earn a small commission, at no extra cost to you. It never changes what the calculator recommends – recommendations are sized to your household, not to the commission. As an Amazon Associate we earn from qualifying purchases.
How much water per person
The calculator uses 3 litres of drinking water per person per day, the figure in official UK guidance. It’s the minimum for drinking – not cooking or washing.
| People | 3 days | 7 days | 14 days |
|---|---|---|---|
| 1 | 9 litres | 21 litres | 42 litres |
| 2 | 18 litres | 42 litres | 84 litres |
| 3 | 27 litres | 63 litres | 126 litres |
| 4 | 36 litres | 84 litres | 168 litres |
| 5 | 45 litres | 105 litres | 210 litres |
| 6 | 54 litres | 126 litres | 252 litres |
Emergency water kit
As well as stored bottled water, a simple emergency water kit gives you a backup if supplies run low:
- Water purification tablets – light and cheap; follow the pack for how much water each tablet treats.
- A water filter – a gravity filter or filter bottle for longer outages. Check it’s rated to remove bacteria.
- A food-grade water container with a tap, for collecting water if your supplier provides bottled water or bowsers.
Storing water
- Shop-bought bottled water is the simplest and safest option.
- If you fill your own containers, use clean, food-grade containers with tight lids.
- Keep water somewhere cool and dark, away from chemicals, fuel and direct sunlight.
- Check best-before dates every six months and rotate bottles into everyday use.
For more detail, read our guide on how much water to store.
Frequently asked questions
How much water should I store per person?
Official UK guidance is at least 3 litres of drinking water per person per day. That’s 9 litres per person for 3 days, 21 litres for a week and 42 litres for two weeks. You’ll need more for cooking and washing.
Does the calculator include water for cooking and washing?
No. It covers drinking water, which is the essential minimum. If you cook food that needs water, or want to wash, store more – or have purification tablets or a filter as a backup.
How much water do dogs and cats need?
A common rule of thumb is about 50 ml per kilogram of body weight a day. A 20 kg dog needs about a litre a day and an average cat about a quarter of a litre. Pets need more in hot weather or if they eat dry food.
How long does stored bottled water last?
Shop-bought bottled water has a best-before date printed on it. Store it somewhere cool and dark, check the dates every six months, and use and replace bottles as they get close.
What if my bottled water runs out?
Purification tablets or a filter can make other water safer to drink. Always follow your water company’s advice – if they issue a “boil water” or “do not drink” notice, do exactly what it says.
More calculators
- Emergency kit calculator
Everything your household needs, in one checklist.
- Power station size calculator
What size power station you need for the devices you want to keep running.
- Power station runtime calculator
How long a power station will run a fridge, CPAP, router or laptop.
- Power bank calculator
What size power bank you need to keep phones charged.
- Emergency food calculator
Calories and meals to store for your household.
- Pet emergency kit calculator
Water, food and supplies for dogs, cats and other pets.
General guidance only – not a substitute for official or medical advice. See every figure we use and where it comes from.