How long can you survive without water? - Life Fiend

How long can you survive without water?

I spend a lot of my time in the country whether its going for a long walk, cycling or running, so water is very important to me. Also, as a prepper, over the years, I’ve tried to calculate how much water I will need to survive during an emergency situation. I’ve described my personal estimates and water storage strategy below.

So, how long can you survive without water? On average, a person can survive without water for about 3 to 5 days, but this can vary depending on lots of individual circumstances. It’s also important to note that dehydration can cause severe health problems long before you actually die from lack of water, so even though you can in theory last several days, you may find that your are unable to function normally long before then.

How much water do we consume every day?

On average, people consume around 2 to 3 litres (64 to 96 ounces) of water per day. However, this can vary based on individual factors such as age, gender, weight, levels of activity, and the climate. 

The Institute of Medicine (IOM) recommends that men consume about 3.7 litres (125 ounces) of water per day and women consume about 2.7 litres (91 ounces) of water per day, which includes water from all sources, such as food and drink. For the purposes of this article, I will go with the average consumption of 2 to 3 litres per day.

What is the total amount of water we need every day?

If we take the average consumption of 2 to 3 litres per person per day, its worth remembering that we also require water for other purposes such as  cooking and for personal hygiene. Also, if you are more active than normal, that will increase your daily requirement and could easily push the required amount up by a couple of litres. 

As the subjects of my blogs are centred around the outdoors or emergency situations, lets come up with some estimates for a typical day and then try to figure out how much we would need to store to keep ourselves relatively safe should the water ever get turned off. 

I’ll assume that we will be quite active and that we will also be using water to prepare two meals per day and a small amount for personal hygiene:

Activity Water per Person per Day
Minimum requirement
Increased levels of activity
Meal - portion of oats
Meal - portion of rice

So for a relatively active person consuming 2 meals per day, they would require 5L of water. That is a gallon of water.

How much water should I store for an emergency?

I’m not sure if there is a correct answer to this question as it is down to your available resources and space. I personally, like the idea of being able to store 6 months of food and water but as you can imagine, to store enough water for a 6 months supply is probably not practical. 

You would need 900L of water and that is just for one person. Families or groups of people living together would need to multiply that amount for each individual.

To give you an idea, the original Jerry Can holds 20L, so that would be 45 Jerry Cans. The space required would be huge along with other considerations such as ensuring the water stays fresh and doesn’t deteriorate from exposure to air, light, and heat, as well as contamination from bacteria, viruses, or other pathogens.

To prevent the water supply from getting spoilt, it’s important to properly store water for long-term storage by using clean, food-grade containers and treating the water with appropriate disinfectants or preservatives. Additionally, it’s recommended to rotate stored water every six months to maintain its quality.

My personal water storage strategy

There are three people living in my house and I have limited space but here is my current supply:

Water Quantity Total Water
2L Bottles
25L Plastic Jerry Cans
Garden Water Butt

The three of us require 5L each per day (total 15L) and I have 350L stored. 

That means I have enough water for us to survive 23 days. That is not a long time but obviously, during that time I could also go out looking for other sources of water.

Its also worth remembering that you don’t necessarily need to store large quantities of water. If there are water sources in your area such a reservoir or rivers, it may be easy for you to go and collect water and bring it back. You will need to be able to filter the water however but that is a topic for another blog. Also, if you live in a populated area, it may the case that several thousand other people have had the same idea as you. This will mean potentially putting yourself at risk from getting into contact with very thirsty and hungry people. I’d rather stay at home and rely on my own store of water.

Even though I have chosen to store several weeks of water at home, I’m also equipped with several filtration methods in case I have to leave my home for whatever reason. Water filters are also a lot more portable than water.  

Something that a lot of people don’t consider is the weight of water. It is heavy and hard to carry around. If we go with our daily estimate of 5L (1 gallon) of water per person per day, that amount alone weighs 3.79 kilograms (8.35 pounds). Add that weight to the rest of your equipment and you can already see that carrying large amounts of water is just not practical.

So what about food? Isn’t that just as important as water?

The short answer is no. 

On average, a healthy adult can survive for several weeks without food and only a few days without water, although this timeline can vary widely depending on the person’s circumstances. The body can derive energy from stored fat and muscle tissue, and the body will initially break down glycogen stores in the liver and muscles to provide glucose for the brain and other essential organs.

In terms of an emergency situation, it is by far the biggest priority to ensure you have enough water to live and only then, concern yourself about food. 

As we are on the conversation about food, its also worth remembering that if you store dehydrated or free-dried food, you will require a fair amount of water to rehydrate it as 90% of its water content will have been removed when it was dehydrated or freeze-dried.

When figuring out the priorities during an emergency situation, I like to think in terms of something called The Rule of Threes. This provides guidance on what your highest priorities in terms of survival.

The Rule of Three's

Note that these are just estimates but is a good way to identify your priorities during an emergency scenario:

You can last 3 minutes without air.

You can last 3 hours without shelter.

You can last 3 days without water.

You can last 3 weeks without food.

So, if you find yourself in a sticky situation such as alone on a desert island, the first thing to ensure is that you have enough air. You should then look to build a shelter and possibly a fire. Now is the time to search for water. Once you have all of those resources covered, then you can start to think about food. 

Obviously there are many different types of emergency that you may find yourself in, whether its stranded in freezing conditions with no heat or shelter, or stuck in a tropical rain forest with water everywhere, so you will need to adjust your priorities accordingly. Water may not be so much of a concern if you are surrounded by fresh water rivers for example. 

There are two other rules but I don’t generally use them but I’ve added them for completeness:

You have 3 seconds to make a decision.

You can last 3 months without love.

The first one assumes that you are in a dangerous situation and only have a few seconds to make a decision to get yourself out of imminent danger. The other is to point out that us human beings are social creatures and we need company. If you go for a few months alone, you may start to go a bit crazy…


Obviously there are many different types of emergency that you may find yourself in, whether its stranded in freezing conditions with no heat or shelter, or stuck in a tropical rain forest with water everywhere, so will need to adjust your priorities accordingly. Water may not be so much of a concern if you are surrounded by fresh water rivers for example. 

But in general, if you need to prioritise between shelter, food and water, use the Rule of Three’s as a guide.

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