Water and food

Store one gallon of water per person per day, for at least three daysHalf for drinking, half for sanitation. Hot climates, children, nursing mothers, and illness all push the number up. Commercially bottled water is the safest and easiest to store.
Add a backup way to make water safe: unscented household bleach or purification tabletsRatio to write on the bottle: 8 drops (1/8 teaspoon) of plain 6% bleach per gallon of clear water, wait 30 minutes.
Stock at least a three-day supply of non-perishable food per personReady-to-eat and no-cook: canned meat and beans, peanut butter, crackers, dried fruit, bars. Favor foods your household already eats — a disaster is a bad time to discover nobody will touch the rations.
Pack a manual can opener, utensils, and paper platesA kit full of cans and no opener is the classic failure mode.

First aid, light, and communication

Assemble or buy a full first aid kitBandages, gauze, tape, antiseptic, tweezers, gloves, pain reliever, antihistamine, and a first aid instruction card.
Pack one flashlight per person, plus extra batteriesStore batteries outside the devices so they can't corrode the contacts. Skip candles — post-disaster fires are common.
Add a battery-powered or hand-crank radio, NOAA weather radio if possibleWhen cell networks are down, broadcast radio is how official instructions reach you.
Add backup phone power: charged power banks or a hand-crank/solar chargerRecharge stored power banks on the same schedule you rotate food.
Pack a whistleThree blasts is the distress signal; a whistle carries much farther and longer than shouting from rubble.
Add basic tools: wrench or pliers, multi-tool, duct tape, work glovesThe wrench is for shutting off gas at the meter — tie it near the kit or the meter, and learn the valve now.
Add dust masks and plastic sheetingFor filtering contaminated air and sealing a room in place.

Copy key documents into a waterproof bag: IDs, insurance policies, bank info, deeds, medical listsAdd a digital set on a password-protected USB drive or in cloud storage. After a disaster these are what rebuild your life.
Include a written contact list and a family meeting planPhones die and numbers live in them. Include an out-of-state contact — long-distance calls often connect when local networks are jammed.
Stash cash in small billsATMs and card readers need power. A few hundred dollars in fives, tens, and twenties buys fuel, food, and lodging when nothing else works.
Add local paper maps with evacuation routes markedNavigation apps need cell towers and battery, both scarce.

Pack sanitation supplies: toilet paper, moist towelettes, soap, garbage bags with tiesBags plus a bucket is the fallback toilet; ties matter more than you'd think.
Add feminine hygiene supplies and personal care items
Pack a change of clothes and sturdy shoes per person, plus warm blankets or sleeping bagsSeason-check the clothes when you rotate supplies — last winter's kit may hold summer clothes.
Add a lighter or waterproof matches in a sealed container

Store at least a week of prescription medications, rotated with each refillAsk your pharmacist or insurer about an emergency supply — many states let you fill early for preparedness. Include a written list of drugs, doses, and prescribers.
Pack spare glasses, hearing aid batteries, and backup medical equipment supplies if medical needsAnything battery- or power-dependent (CPAP, oxygen, mobility) needs a written power-outage plan.
Add infant supplies: formula, bottles, diapers, wipes, rash cream if infantsSize up the diapers when you rotate — babies outgrow the kit fast.
Add pet supplies: three days of food, water, medications, leash, carrier, vaccination records if petsMany shelters only take pets with proof of vaccination.
Duplicate a smaller go-bag version for each car and workplaceDisasters don't wait for you to be home. The car kit adds jumper cables, a blanket, and seasonal gear.

Store the kit in portable containers in a cool, dry, known spotBins or backpacks everyone in the household can find in the dark. Tell everyone where it is.
Set a twice-yearly calendar reminder to service the kitTie it to daylight saving clock changes so it actually happens.
At each service: replace expiring food, water, and medications; recharge power banks; re-fit clothesCheck can dents and swelling, battery corrosion, and document currency. Replace commercially bottled water by its date.
Re-evaluate the kit after any household changeNew baby, new pet, new prescription, new address — each one changes what three days of self-sufficiency looks like.