Food Storage Duration Calculator

Work out how many days your stored food really lasts from your household size, a per-person calorie figure, and the total calories on your shelves.

How food-storage math really works

The honest answer to "how long will my food last?" is a division problem: the total calories on your shelves, divided by the calories your household actually eats in a day. Everything else - the buckets, the labels, the "1-year supply" branding - is packaging around that fraction. A household of four eating a standard 2,000 calories per person burns 8,000 calories a day, so a kit sold as "30 days" but built on 1,500-calorie rations for one person covers that family for under six days. The calculator above runs the division on your numbers, not the label's.

Where do the inputs come from? People is everyone eating from the stores, including guests you would realistically feed. Calories per person per day is a planning figure: 2,000 is the standard label value used by the FDA for nutrition math, and it is a sensible default; heavy outdoor work in cold weather can push real needs well above it, which is an argument for rounding your target up, never down. Stored calories is the sum of the calorie counts printed on what you own - a food-storage spreadsheet or an afternoon with a notepad gets you the figure once, and updating it takes minutes.

The output leans conservative on purpose. Coverage rounds down, because 7.95 days of food is not 8 days when day 8 is the one that matters. The two targets shown with your result are the planning anchors used across this site: a 3-day minimum (the classic 72-hour kit, sized for evacuation or a short disruption) and a two-week supply, which is the shelter-at-home figure preparedness agencies recommend working toward. Ready.gov frames both the same way: build the small kit first, then extend it.

What the number does not tell you: whether the calories are edible under stress (a pantry of only dry beans needs fuel and water to become food), whether they rotate before they expire, and whether anyone in the house will actually eat them. Those are the questions the guides below take on - start with the 72-hour kit math and rotation, then pair this result with the water storage calculator, because stored food without stored water is a plan with a hole in it.

Worked examples

Frequently asked questions

How long will my stored food actually last?
Divide the total calories on your shelves by your household's real daily burn. A household of four eating 2,000 calories per person per day goes through 8,000 calories every day, so a '30-day' kit built around 1,500-calorie days quietly becomes an 11-day supply for that family. The food storage calculator does this arithmetic from your own numbers instead of a marketing label.
How much water should I store?
FEMA and Ready.gov say to store at least one gallon per person per day, covering roughly half a gallon for drinking and half for sanitation, with a minimum of a three-day supply and two weeks recommended for sheltering at home. Four people for two weeks is 56 gallons, which is the arithmetic most people have never actually run. The water calculator also converts the total into real containers.
What size generator do I need?
Add up the running watts of everything you want powered at the same time, then add the single largest starting surge among your motor-driven appliances (refrigerators, sump pumps, furnace fans can briefly draw about three times their running draw). The generator calculator does both steps and adds sizing headroom, so you buy for the surge you will actually see rather than a guess.
Are these calculators a substitute for official guidance?
No. They apply published planning rules from FEMA, Ready.gov, the USDA, and the CPSC to your household's numbers, and every tool page cites the rule it uses. For live emergencies, follow the instructions of local emergency management, and treat these results as planning arithmetic, not a guarantee.
Why do the results lean conservative?
Because in preparedness the cost of the two errors is not symmetric. Storing 10% more water than you needed costs shelf space; storing 10% less costs you on day twelve. Where the tools round, they round in the direction that leaves you with margin - up for what you need, down for what your stores will cover.
Do I need to buy special survival food for any of this?
No, and the calculators do not assume it. Calories are calories to the arithmetic: a pantry of rice, beans, canned goods, and peanut butter counts exactly the same way a freeze-dried kit does. The guides compare the real economics of both approaches so you can decide with numbers instead of fear.
Is my data stored anywhere when I use these tools?
No. Every calculator runs entirely in your browser as a static script. Nothing you type is transmitted, logged, or stored anywhere; reloading the page resets it.

Preparedness guides

The calculators answer "how much"; these guides answer "why" and "how". Original, plainly written articles covering the knowledge behind the numbers - no fear, no hype, and no products to sell you.