Emergency Food & Water Supply Calculator (household stockpile by days)

Understanding the emergency food and water supply calculator — concept and principle

This calculator works out how much drinking water and food energy a household should store for an emergency such as a storm, flood, earthquake or long power cut. It turns the official water guideline and a daily calorie figure into totals you can shop for.

Two weeks for three people: with the default inputs the result is 159 L water (16 containers · 84,000 kcal).

How it is calculated

Water (US gallons) = people × days, at one gallon per person per day.
Water (litres) = gallons × 3.785411784.
Containers = litres ÷ container size, rounded up.
Food energy to store (kcal) = people × days × kcal per person per day.
Food energy per person = days × kcal per day.
The calculator also checks that you plan for at least the 3-day minimum.

The principle

US preparedness guidance (Ready.gov, run by FEMA) recommends at least one gallon of water per person per day, for drinking and basic hygiene, for at least three days. A gallon is about 3.8 litres; much of it is for drinking, the rest for washing and food preparation. Food is counted as energy because people need a steady calorie intake to stay warm and think clearly under stress. The default 2,000 kcal per day is the reference figure used for general nutrition advice on US food labels. Totals scale simply with people and days, so doubling the days doubles the supply.

Worked example

Default inputs: 3 people, 14 days, 2,000 kcal per person per day, 10 L containers.

Water = 3 × 14 = 42 US gallons = 42 × 3.785 = 159.0 L, shown as 159.
Containers = 159 ÷ 10 = 15.9, rounded up to 16.
Food energy = 3 × 14 × 2,000 = 84,000 kcal.
Per person = 14 × 2,000 = 28,000 kcal.
14 days ≥ 3, so the 3-day minimum is met: yes.

Each point is the calculator re-run with only “Days to prepare for” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Days to prepare for	Drinking and hygiene water (L)
3.5	40
7	79
10.5	119
14	159
17.5	199
21	238
28	318

How to read the result

Turn the calorie total into foods by reading the energy per pack on labels: for example, a 400 g tin listing 300 kcal per half tin gives 600 kcal. Choose foods that keep without a fridge and need little water or cooking, and include foods your household will actually eat. Children, people who are nursing or ill, pets and hot weather all raise water needs, so add extra. Store water in clean, food-grade containers and rotate food before it expires.

Common mistakes

Forgetting water for cooking dried foods such as rice or pasta.
Storing only snacks; aim for a mix of protein, carbohydrate and fat.
Ignoring special diets, baby formula and medicines.
Buying once and never checking dates.

Keep in mind: Follow official advice for your area; some agencies recommend longer supplies. This is a planning aid, not a full emergency plan.

Frequently asked questions

How much water should I store per person?

At least one US gallon (about 3.8 L) per person per day, for at least three days.

How many calories should emergency food provide?

The calculator uses 2,000 kcal per person per day by default; active adults and teenagers may need more, small children less.

How long should my emergency supply last?

At least three days is the US minimum; some emergency agencies advise longer, so check local guidance.

Sources: FEMA Ready.gov, "Water" and "Food" (emergency supply guidance) · US FDA, 21 CFR 101.9(d)(9) (2,000 calories used for general nutrition advice)

Checked 9 Nov 2026. FEMA Ready.gov, “Water” (one gallon of water per person per day, at least a three-day supply; archived page) and “Food” (at least a several-day supply of non-perishable food); 2,000 kcal reference: US FDA, 21 CFR 101.9(d)(9) (“2,000 calories a day is used for general nutrition advice”).

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