How it's calculated
Everything on your list comes from three public sources: Ready.gov, the CDC and the American Red Cross. We copy their numbers and words; we don't make up new ones. Each line on the list links to the exact quote on our sources page.
- Water: 1 gallon per person per day, for drinking and sanitation. People × days = gallons. We also show liters (× 3.785) and cases of 24 × 16.9 oz bottles, rounded up so you never buy short.
- Days: the Red Cross says 2 weeks if you stay home and 3 days in a go-kit if you evacuate. The calculator picks that for you until you choose a number yourself.
- Food: non-perishable food that needs no cooking or refrigeration, counted in person-days (one person for one day), plus a manual can opener.
- Medicine: the Red Cross hurricane page says to have a 1-month supply in a child-proof container, and at least 7 days in your kit. Ask your pharmacist about early refills.
- Pets: CDC lists 2 weeks of food, water and medicine for each animal, plus a carrier for each pet if you leave.
Some things have no official number: how much cash, how many batteries, how many flashlights, how much water a pet drinks, how many diapers a baby uses. For those we print no number, or we say clearly that it's our suggestion (1 flashlight per person, not counting babies).
Example: a family staying home
Two adults, two children and a baby staying home for 14 days: 5 people × 14 days = 70 gallons of water, about 265 liters, or 23 cases of bottled water. That is also 70 person-days of food. If it's very hot, Ready.gov says water needs can double, so up to 140 gallons.
The same family evacuating with a 3-day go-kit needs 15 gallons of water and 15 person-days of food, plus a carrier for each pet and a full tank of gas.
Water is heavy: a gallon weighs about 8 pounds. If you can't carry it all, fill clean containers and bathtubs at home before the storm, and keep bottled water for the go-kit.