How Much Water Per Day for Survival?
The complete guide to emergency water storage - how much to store, how to store it, and how to purify water when you need it.
TL;DR:
Store 1 gallon of water per person per day as your baseline. For a 2-week emergency supply, that's 14 gallons per person. In hot weather or for active adults, plan for 1.5-2 gallons. Use our Cistern Size Calculator to find your exact storage needs.
The Quick Answer
According to FEMA and Ready.gov, the standard recommendation is one gallon of water per person per day. This covers:
- Half a gallon for drinking
- Half a gallon for cooking and basic hygiene
For a 3-day emergency kit (the minimum), that's 3 gallons per person. For serious preparedness, aim for a 2-week supply: 14 gallons per person.
This is a survival minimum. In hot weather, with heavy activity, or for nursing mothers and children, you'll need more.
Daily Water Needs Breakdown
| Use | Amount | Notes |
|---|---|---|
| Drinking | 0.5-1 gallon | More in heat or with activity |
| Cooking | 0.25-0.5 gallon | Rehydrating food, making coffee |
| Basic hygiene | 0.25-0.5 gallon | Hand washing, brushing teeth |
| Dish washing | 0.5-1 gallon | Minimal, with conservation |
| Total (Survival) | 1 gallon | FEMA minimum |
| Total (Comfortable) | 2-3 gallons | Includes basic sanitation |
Critical Rule
Never ration drinking water unless authorities explicitly tell you to. Dehydration impairs judgment and physical ability. Drink what you need and focus on finding more water.
Water Storage Chart by Family Size
Use this chart to calculate how much water to store based on your household size and preparedness goals.
| Household | 3 Days | 1 Week | 2 Weeks | 1 Month |
|---|---|---|---|---|
| 1 person | 3 gal | 7 gal | 14 gal | 30 gal |
| 2 people | 6 gal | 14 gal | 28 gal | 60 gal |
| 4 people | 12 gal | 28 gal | 56 gal | 120 gal |
| 6 people | 18 gal | 42 gal | 84 gal | 180 gal |
Calculate your exact needs with our Cistern Size Calculator.
Factors That Increase Water Needs
Climate and Weather
Hot weather dramatically increases water needs. In summer heat, plan for 1.5-2 gallons per person per day. Humidity also matters - dry climates cause faster dehydration through respiration.
Physical Activity
Heavy labor or walking long distances can require 2-3 times more water than sedentary activity. If your emergency plan involves bugging out on foot, account for this.
Special Populations
- Nursing mothers: Need extra fluids for milk production (add 0.5-1 gallon)
- Young children: Dehydrate faster, may need more frequent small drinks
- Elderly: May not feel thirst signals, need reminders to hydrate
- Sick individuals: Fever, vomiting, or diarrhea dramatically increases fluid needs
Pets
Don't forget your animals. Dogs need about 1 ounce of water per pound of body weight daily. A 50-pound dog needs about 0.4 gallons per day.
Medical Needs
Some medications require water to take. Dialysis, wound care, and certain medical conditions require additional clean water. Plan for these specific needs.
Water Storage Options
Commercial Bottled Water
The easiest option. Commercially bottled water stays safe for 1-2 years unopened. Stock cases of bottled water and rotate through your supply by using and replacing them.
- Pros: Convenient, portable, already purified
- Cons: Expensive for large quantities, takes up space
Water Bricks and Containers
Stackable, food-grade containers designed for water storage. Popular sizes are 3.5 and 5 gallons. They're easy to move and store.
55-Gallon Drums (Blue Barrels)
The go-to for serious water storage. One drum covers one person for almost 2 months. Use food-grade barrels with a bung wrench and siphon pump.
- Fill with tap water (already treated with chlorine)
- Add water preserver for 5-year storage life
- Store in cool, dark location on a pallet (not concrete)
Rainwater Collection
A sustainable option for long-term preparedness. One inch of rain on a 1,000 sq ft roof yields about 600 gallons.
Calculate your potential with our Rainwater Collection Calculator.
Water Purification Methods
If you need to use water from unknown sources, you must purify it first. Here are the main methods:
Boiling
The most reliable method. Bring water to a rolling boil for 1 minute (3 minutes above 6,500 feet elevation). Kills bacteria, viruses, and parasites.
Chemical Treatment
- Bleach: 8 drops of regular unscented bleach per gallon. Wait 30 minutes.
- Iodine tablets: Follow package directions. Not for pregnant women or those with thyroid issues.
- Water purification tablets: Chlorine dioxide tablets are effective and have a long shelf life.
Filtration
Removes sediment, bacteria, and parasites. Quality varies widely. Look for filters rated to remove bacteria (0.2 microns or smaller). Popular options include Sawyer, Berkey, and LifeStraw.
Use our Water Purification Calculator to determine treatment amounts for your water source.
Frequently Asked Questions
How much water does one person need per day in an emergency?
FEMA and Ready.gov recommend one gallon per person per day as the baseline. Half is for drinking, half for cooking and hygiene. In hot weather or with increased activity, plan for 1.5-2 gallons per person per day.
How much water should I store for a family of 4?
For a 3-day emergency supply: 12 gallons (4 people x 1 gallon x 3 days). For a 2-week supply: 56 gallons. For a 30-day supply: 120 gallons. Add extra for pets, medical needs, or hot climates.
How long can you survive without water?
Most people can survive only 3-5 days without water, though this varies based on temperature, activity, and health. Dehydration symptoms start within hours. Never ration water during an emergency - drink what you need and find more.
What is the best way to store water long-term?
Commercially bottled water lasts 1-2 years unopened. For bulk storage, use food-grade containers (blue barrels, water bricks) with water preserver additive for 5-year storage. Store in cool, dark locations. Rotate home-stored water every 6 months.
Can I drink rainwater in an emergency?
Rainwater is generally safe if collected in clean containers, but should be filtered and purified before drinking. It can contain pollutants, bird droppings, or roofing materials. Use a proper filter and purification method - boiling, UV, or chemical treatment.
Calculate Your Water Storage Needs
Enter your household size and preparedness goals to get an exact storage target.
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