80: Calculating Your Daily Water Consumption Needs

Calculate how much water you will need each day to survive
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Today’s question about daily water consumption comes to us from Jason in VA.  Jason writes:

Hi Brian,

I listened to the Water Storage podcast yesterday. It was really good.

I wanted to get your opinion on my water storage.

We have a household of 5. I have built up to 20 cases of water along with 20 – 1-gallon jugs of water. I do keep a large trash can full of water outside available for when the power goes out so I can flush my toilets.

I feel like I should be good for almost a month with my current supplies for general hygiene, drinking, and cooking. My outside supply of water would probably last several days to flush the toilet.

Anything longer than a month, I feel like I should be able to collect enough rainwater to keep going if necessary. I also have a stream about a mile away that I could walk to get water. Not ideal but would do it if I needed to.

I have multiple ways to boil water that I collect when the power is out.

Do you think I am on the right track? I would love to hear your suggestions on other things to consider.

Jason in VA

How Do You Calculate Your Daily Water Consumption Needs?

First off Jason, yes, I think you are definitely on the right track with your daily water consumption. As with most preppers, you have probably done more than 99% of the population when preparing for the hard times ahead. After all, as preppers, we know that it’s not a matter of if something terrible will happen, but rather when something terrible will happen.

When it comes to figuring out your water storage prepping and how much water you should have on hand, you first need to determine how much water your family will need daily.

To establish our daily water needs, let’s consider the National Academies of Sciences, Engineering, and Medicine’s recommendations, stating that men need 101 ounces of water per day (~13 cups). In comparison, women need 74 ounces of water each day (~9 cups).

8 Eight-Ounce Glasses of Water Is a Myth

It’s worth mentioning that based upon our fundamental needs, the often-referred-to recommendation that we should consume 64 ounces of water per day falls short. This helps remind people who would otherwise not drink much water but leaves women with over an eight-ounce per day deficit and men with a nearly five glass per day deficit.

With the basic water intake needs of an adult set, it’s critical to consider the situation for which each of you is planning. Those considerations matter because without their inclusion into your preparedness plan, you may find yourself with a less sustainable supply of water than you had hoped.

Some Scenarios Require Even More to Meet Daily Water Consumption Needs

Some individual considerations that you may want to consider when creating your water plan include age, environmental conditions, stress, expected physical exertion, and health and fitness levels among group members.

Women who are pregnant or breastfeeding, require additional water. Pregnant women should drink 108-ounce glasses of water per day, while breastfeeding women may need a daily water intake of up to 104-ounces (13-cups).

Planning the water needs of children requires people to be flexible and attentive as their needs change over time.

Without individual considerations such as environmental impacts, Children’s Hospital of Orange County recommends that children one year of age and older intake one cup of water each day, per year of age. So, for example, a one-year-old should drink one cup of water per day, while a seven-year-old should drink seven cups of water per day.

Another consideration with children is how to get them actually to drink enough water each day. One method is to encourage children to take small, frequent sips of water throughout the day. You can also try to make drinking water fun and turn it into a game. Regardless, take the time and effort to make sure children stay hydrated.

Additional Factors

It’s critical to stay on top of the factors that may increase your daily water demand. Some of the issues that may raise your daily requirements are weather, temperature, altitude (8,000+ feet), and illness such as fever, diarrhea, or vomiting.

Exercise and physical exertion also increase water needs, particularly during hot weather or at high altitudes.

It’s critical in all of these cases to have enough water available to avoid dehydration which can become deadly if it’s extreme.

Is There Enough to Meet Your Daily Water Consumption Needs?

Now that we know what each person’s daily water needs are, let’s see what you have on hand.

I assume your twenty cases of water contain the typical twenty-four, 16.9-ounce bottles. If so, each case of water holds just over 3 gallons of water. Next, we’ll add up your twenty individual gallons of water and a ninety-six-gallon trash can of water. This all adds up to just shy of 180-gallons of water.

So, Jason, without knowing the ages of your children, I’m going to err on the side of caution and assume your situation necessitates a high daily demand for water. Therefore, the following calculations for your minimal water consumption needs are based upon you, your wife, and three teenage sons.

My water consumption calculations tell me that you’ll need just over four gallons per day to meet your family’s daily water consumption needs. Factor in the water you have on hand, and you have about nineteen days of water stored and ready for your family’s hydration needs.

Remember, You Need Water for More Than Drinking

Don’t forget that you have 19 of drinking water. Any time you consume water for anything other than drinking, you reduce your total drinking water supply.

One way to look at non-drinking water use is like this. If your toilet uses two gallons per flush, and you flush it twice per day, you’ll use an extra four gallons of water each day. Add up water for used cooking, cleaning, washing dishes, and flushing the toilet. You can quickly burn through an additional 10-gallons of water per day, if not more.

The Shocking Truth About Water Use During Disasters

This is where the truth about our concept of water use sets in. Combine your daily drinking requirements of 4.2-gallons with your approximate 10 gallons per day non-drinking water usage. You’ll end up with a total estimated daily water usage of about fourteen gallons.

Compare your overall on-hand water storage of 180-gallons to your daily usage. My estimates show that you should have just over twelve days of water available. This is less than the month that you are aiming for.

While the reality of your situation may be surprising, you are much better off than most people. You’re also not far from achieving your goal. One other option to look at when working to increase your self-reliance by adding a Water Bob to your preps. That alone has the potential to add another 100-gallons (10-days) of water to your current supply. They’re inexpensive and you can get one for every bathtub in your home. Check out this article on long-term water storage for more inexpensive and helpful ideas to store water.

The Bottom Line on Daily Water Consumption

As for your question asking if you’re on the right track, yes, I think you are. I also think you should take a little bit of a harder look at your daily water consumption needs.  Think about all the ways you use water that doesn’t include drinking (and don’t forget your pets!) Then, come up with some other methods of storing additional water. Doing so will help you make it through the next difficult time.

Leonardo da Vinci stated:

“Water is the driving force for all nature.”

And yes it is. We can’t live without it, but at the same time, it can be a deadly foe. So, make sure you have complete plans for all of your water needs.


Stay safe, 


  1. Margaret Quintana on February 19, 2020 at 9:32 pm

    How much water should I consume daily,I am a diabetic. My kidneys are what my Dr. says are at base level. Will increasing my water consumption help keep my kidney function at a healthy level. What does base level mean? I’ve increased my water from 4 bottles (16.9oz) to 5 bottles daily, should I be drinking more? I’m a diabetes tablet (glimperide 4mg.) Once a day. I need to continue losing weight. I would appreciate your opinion.

    • Brian Duff on May 6, 2020 at 9:34 pm

      Hello Margaret,

      I feel that your best option is to speak with your doctor.

      They will be able to give you the best advice possible!

      Stay safe!

  2. Mic on September 17, 2021 at 12:21 pm

    Excellent article.
    This is something that the Prepper community needs to hear and understand.
    To many of them seem to think that they can survive on 1 gallon a day, per person, for ALL their water needs.
    To few Preppers do any real research and they most just follow others (sheep), and we know what happens to Sheep, they get slaughtered.

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