Survival Water Requirement Calculator

Work out survival water requirement instantly with clear inputs, formula shown and shareable results.

About Survival Water Requirement Calculator

Emergency guidance is about one gallon or 3.8 litres per person per day covering drinking and basic sanitation, and water weighs one kilogram per litre. The weight figure is what makes the plan realistic: a week for four people is over a hundred kilograms, so storage location matters as much as quantity.

Formula

Water needed

litres = people x days x litres per person per day

Worked example

With the default values below, Survival Water Requirement Calculator returns Water to store of 106.4. Change any input above and every figure here is recalculated in your browser.

Inputs used

Number of peopleminimum 1: 4
Days to prepare forminimum 1: 7
Water per person per dayminimum 0.1 L: 3.8 L
Container sizeminimum 0.1 L: 20 L

Results

Water to store: 106.4 L
Containers needed: 6
Weight of that water: 106.4 kg
Drinking water alone at 2 L a day: 56.0 L

Step by step

1Values used
2Water needed
3Water to store= 106.4 L
4Containers needed= 6
5Weight of that water= 106.4 kg
6Drinking water alone at 2 L a day= 56.0 L

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Survival Water Requirement figure worked out?

litres = people x days x litres per person per day. Emergency guidance is about one gallon or 3.8 litres per person per day covering drinking and basic sanitation, and water weighs one kilogram per litre.

Why does this matter?

The weight figure is what makes the plan realistic: a week for four people is over a hundred kilograms, so storage location matters as much as quantity.

What do I need to enter?

Enter number of people, days to prepare for, water per person per day, container size. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.