Water Storage Calculator

Water Storage Calculator

A water storage calculator tool used to determine how much water you need to store for emergencies and disasters.

This is a dynamic guide curated by all of our authors. Our Water Storage Calculator is constantly being updated with up to date and accurate information, so please check back frequently for updates.


Water is a basic human need and key for survival. Methods to gather, store, and sanitize water are all important but knowing how much water you may need is important as well. Water is heavy and takes up a lot of space when it is stored, so knowing exactly how much you need can help you plan for preparedness.


Contents (Jump to a Section)


Water Storage Calculator

Water is an extremely important resource during emergencies and disasters, so it is always a good idea to know where you stand beforehand. That’s why we developed the tool below- to make it easy to understand how much water you need depending on the length of time and the number of people you are planning for.


How Much Water Should You Store for Emergencies?

30 gallons per month, per person is the consensus of the CDC, FEMA, and most emergency management agencies.

While the amount of water that you need depends on your planned uses, they break down pretty easily:

Drinking- People generally need 15 gallons of clean drinking water per month. Your body is constantly losing water through sweating, digestion, and even breathing. You will need an ample supply of water to prevent dehydration.

Cooking– About seven and a half gallons of water are needed to use for cooking per month. Most freeze-dried food kits require water for rehydration. Water is also needed to activate MRE heaters. Boiling is an effective cooking method that requires water as well.

Washing– Hygiene is important during emergencies, and seven and a half gallons are needed to keep clean, wash hands, and for first aid use.

If you use the calculator above, you can plan ahead using these amounts to find exactly how much water you need to store.


How Frequently Should Water Storage be Rotated?

The storage container type, condition of the water, and conditions of the storage area all affect how often you should rotate your water supply.

Different types of plastic storage containers are effective for different lengths of time. BPA-free plastics are preferred for long-term water storage because BPA can leach into the water, and BPA mimics estrogen and can effect your body.

Purified and/or treated water is best for storage and would only need to be rotated out every five years. Still, it should be checked for algae growth or any contaminants or murkiness annually. Any sort of film or discoloration is an easy way to tell that you need to rotate the water out.

Water stays best in airtight, watertight containers stored out of sunlight in a room temperature setting. Temperature fluctuations can encourage bacteria growth, compromise the seal on containers (through pressure release), and degrade plastics. If you are not storing water in ideal settings, you will need to check the water more often and rotate it out more frequently.


How to Sanitize Water

Sanitizing water is a very important skill to learn, and is easiest with a few resources. There are many different methods, but most methods revolve around first filtering the water of contaminants and then treating the water- creating a two step process. Most people treat water with bleach, tablets, or drops- but there are also newer methods using UV light.

Sanitizing Water with Filters

Different types of filters have varying degrees of effectiveness. Filters count as anything from a mesh keeping leaves out of your rain barrel to a sophisticated reverse osmosis filter. Even high filtration devices (like osmosis filters and survival filters) will need treatment when preparing water for long term storage. Water storage needs to be treated to prevent growth, not just to immediately provide clean water.

Lifestraw Water Filter
Filters have come a long way, but aren’t a complete solution.

Sanitizing Water with Bleach

Using typical household bleach (non-scented), the amounts the CDC recommends depends on whether the water is clear or cloudy.

Amount of Water1 gallon55 gallons300 gallons1000 gallons
Bleach for Clear Water8 drops2 1/2 tablespoons3/4 cup2 1/2 cups
Bleach for Cloudy Water16 drops5 tablespoons1 1/2 cups5 cups
Using household bleach (non-scented) with 5.25 – 8.25 chlorine content.

Bleach is a versatile chemical for emergencies, making it one of the preferred water treatment methods.

Sanitizing Water with Tablets or Drops

Purification tablets or drops make water sanitization even easier. Potable Aqua is the most common tablet brand and our top pick. The treatment tablets act quick with water ready to drink in 35 minutes.

Aquamira is the most common drop brand and is a solid choice as well. It takes at most 30 minutes to treat, and is a very effective chlorine dioxide treatment solution.

Both of these can be used to treat turbid water, or to clean water in preparation for long term storage.


How to Collect and Store Water

Gathering and storing water is no small task. Water is bulky, heavy, and liquid is generally hard to store. You can only store so much water until it becomes unreasonable to keep it treated, rotated, and fully reliable so water collection methods are important for long term plans. A few ways people collect water include:

  • Rainwater Collection – extremely popular with preppers, rain barrel systems can work in a wide range of applications and can use your roof area to collect massive amounts of water whenever it rains.
  • Wells – one of the oldest and reliable methods is well digging. It may require a homestead or rural plot, but wells make you more self-sufficient when you are not reliant on city/suburban water mains.

Some of the top storage methods include:

  • Water Bottles/Jugs– Easily bought and stored from grocery stores, they make for easy shorter term water storage.
  • Temporary Storage– tools like the WaterBOB, or just gathering water in storage containers and bathtubs can be helpful when preparing for impending disasters.
  • Water Pouches– Ideal for bug out bags and other mobile emergency kits, water pouches are easy on-the-go solutions and have a long shelf life.
  • Water Bricks and Drums– Reusable large water storage containers are ideal for preparedness ranging from 3 months to a year.

There are other great ways for collection and storage, like dew collectors and giant water tanks- but those are less common than the methods above.


The Next Step

Emergency water storage should be a priority for everyone, just like prepping. If you are unfamiliar with prepping or what preppers are, check out: What is Prepping and What is a Prepper?

Hopefully, our water storage calculator helped you determine how much water you need to store, or helped you verify your current water storage. The survival rule of 3 states that you can’t go much past 3 days without water, so it’s best to use 3 days as a starting point if you are just starting out with the calculator and water storage.

Once you have water and food storage down, check out what else you need to round out your preparedness with our comprehensive survival kit guide.

Emergency Water Storage Calculator