How Much Water Should You Need To Drink A Day? Hydration Calculator

Reviewed by Elizabeth Gonzalez Cueto, MD

A team of qualified and experienced fact-checkers carefully reviews our content before it is published on our website. At MIDSS, we rely on the latest and most reliable sources, which are cited in the text and listed at the end of each article. We also do not accept plagiarised and misleading content from our authors and contributors. Read more about our fact check and editorial process.

how much water should you drink a day

The National Academy of Medicine[1] says men should drink 101 oz of water daily, and women should drink 74 oz per day. And it can come in any and all fluids you have for the day, such as milk, coffee, sports drinks, and other beverages.

However, even if these numbers are accurate, they are still averages. Individual requirements vary widely. So, how can you determine exactly how much water you require?

How Much Water Should You Need?

People with certain health conditions need higher daily fluid intake to prevent dehydration. Physical activity, hot weather, and digestive system problems can affect how much water you need.

So…how much water should you drink? Consider these three steps:

  • Calculate your base hydration needs by dividing your weight in pounds in half. This is how many ounces you should start with each day.
  • Consider your activity level and environment. Are there reasons you may need more water than usual? Are you catching up from yesterday? Or have you hydrated in preparation for exercise?
  • Track your average intake. How much water you should drink varies from day to day, but you’ll start to notice patterns if you pay attention. Drink when you’re thirsty, when your lips are dry, or when your urine turns dark.

What Happens If You Don’t Drink Enough Water?

If you don’t drink enough fluid daily, it may negatively affect all aspects of your health. More severe dehydration is a medical emergency. Symptoms[2] of severe dehydration include:

  • feeling thirsty
  • feeling dizzy or lightheaded
  • feeling tired
  • a dry mouth, lips and tongue
  • sunken eyes
  • dark yellow, strong-smelling urine
  • peeing less often than usual

The overall health consequences of dehydration can lead to serious illness and even death.

how much water should you drink a day

What Factors Affect Fluid Needs?

The central nervous system (CNS) and neuroendocrine hormones work constantly to maintain internal homeostasis through a complex network of many organ and neural systems. This is needed to keep normal physiological functions (like blood pressure, pH, and body temperature) and good health, as well as to deliver essential substances (like oxygen, water, glucose, sodium, and potassium) to cells. Several things that affect the body’s water balance are controlled by the CNS.

The answer to the question ‘How much water should you drink each day?’ depends on various factors. Here is a list of some common ones:

Body Weight

Your weight is one of the biggest variables in deciding how much water you should drink daily. Here’s a simple equation[3] to help you calculate your base goal:

Take your weight in pounds, halve it, and drink that number of ounces of water.

Example: 160 lbs x ½ = 80 ounces of water per day.

It’s that easy! Half an ounce of water per pound of body weight is a good starting point. However, other factors may affect whether you require additional fluids.

Birth Sex

Men generally need[4] more water per pound of body weight than women. Healthy females typically have a higher percentage of body fat than healthy males. Fat has much less water than other types of tissue and needs less to function.

However, hydration is harder at certain moments in a woman’s life. Women of reproductive age lose vital fluids and micronutrients through regular blood loss. While they are menstruating, they need to drink more water.

Pregnant and lactating individuals also have greater hydration needs. Breast milk is typically 87% water[5].

Life Stage

Many factors impact your hydration levels. Looking at your life stage may help predict some of those factors.

  • Children and teenagers grow rapidly. They also tend to be more active. These traits make them thirstier.
  • Adults, meanwhile, don’t have the metabolic burden of growing. They tend to live more sedentary lives in buildings that are temperature-controlled.
  • Elderly individuals feel less thirst, putting them at higher risk of dehydration.

Diet Quality

A diet rich in fresh fruits and vegetables is the best way to maximize water ingestion. About 20%[6] of your daily water intake comes from your food.

You also want to be aware of your intake of salt[7], caffeinated beverages, and alcohol[8], since these substances cause fluid loss. They should be the first to go if you’re struggling to stay hydrated.

Eliminating caffeine or alcohol consumption may be very difficult, but at least it’s easy to know how much you have. Salt is much more challenging to track. It’ss in almost everything we eat, especially processed and prepackaged foods. According to the CDC, 70% of all the salt[9] Americans consume comes from restaurants, prepackaged and processed foods.

So if you’re losing fluids due to salt, it is important you pay attention to the salt content you add in your meals, likethat bagel, McDonald’s hamburger, canned soup, and even instant pudding!

Activity Level

Activity burns calories throughout the day. You need water to process calories and generate sweat to manage your body heat. The more active you are, the more water you’ll need to replace. This is even more true if you’re active in hot temperatures.

You can find countless reports about how much water you should drink after exercise performance. Recent research[10] suggests that evaluating the color of your urine before and after exercise is the best indicator of your post-exercise fluid needs. You want your pee to always be light yellow.

Benefits of Drinking Water Throughout the Day

Here you will learn how drinking adequate amounts of water benefit your health.

Heart Health

Cardiovascular disease is the leading cause of death worldwide, and research suggests that hydration reduces the risk[11] of heart failure. Drinking too little water can cause increased salt in the blood, which strains the heart. Proper hydration allows your body to regulate fluids and blood pressure.

Brain Health

Having adequate water intake helps improve brain function. In general, staying hydrated helps to stabilize moods and reduce stress. You need water to eliminate the excess hormones and neurotransmitters in your system. Research suggests that even moderate dehydration interferes with the brain’s ability to concentrate[12].

Kidney Health

Chronic dehydration can cause the accumulation of minerals in the kidney, known as kidney stones. The stones pass through the urethra, painfully tearing things up on the way out. Adequate fluid intake can prevent this[13] and also reduce inflammation after it happens.

Joint Health

Sufficient hydration helps to reduce inflammation[14] everywhere in the body, particularly after intense exercise. Many people struggle with inflammation in their joints. As we age, joint health and mobility often decline. Healthy joints comprise over 80% water[15], so maintaining healthy fluidity should help relieve and prevent joint pain.

Healthy Weight Maintenance

Drinking water doesn’t cause you to lose weight on its own. However, drinking water does help with weight loss. How much water should you drink a day to lose weight?

First of all, when you’re hydrated, you eat fewer calories. Hydrated people tend to feel less hungry. And you’re also likely to eat less if your stomach is full of zero-calorie liquid. This results in you eating less, having fewer cravings, and feeling more energetic.

You also need extra water when your body breaks down and removes excess fat. Finally, being dehydrated will cause your body to retain excess water, increasing the number on your scale.

Does water intake affect your Energy Levels?

Water affects energy enormously. In fact, a new study[16] from Clinical Endocrinology reveals that drinking sufficient plain water can increase cellular metabolism by 30%. People suffering from dehydration say they feel tired or sluggish. Staying hydrated helps keep your cells running efficiently. It especially helps with nutrient transport and flushing waste. Staying hydrated is a great way to boost energy levels[17] quickly!

Temperature Maintenance

Water plays an important part[18] in managing body temperature, particularly if you’re living in a dry climate. If enough fluid is moving through our system, we can maintain homeostasis for the body and maintain an appropriate body temperature. This happens through blood circulation to distribute heat and release water through the skin in sweat.

Mood Maintenance

You’ve undoubtedly encountered someone who was “hangry.” Many can attest that if your blood sugar is low, you may feel grouchy or intoxicated. A similar thing can happen with dehydration. Even mild dehydration-as little as 1%[19], barely causing thirst-led women to experience poor moods.

Skin Health

Your skin is your largest organ, and it needs water to do its job. The skin acts as a barrier to keep dangerous things outside your body. It also gets rid of metabolic waste through sweat. It can’t do either of those things if you’re dehydrated. Poorly hydrated skin can result in dryness, wrinkles, and breakouts. So ditch the expensive skincare routine and start drinking more water!

Immune System

Insufficient fluid ingestion can weaken your immune system. Sweating is vital to preventing overheating when you have a fever. Your armies of white blood cells don’t do as well if your systems are all sluggish because you’re low on fluids. In the post-pandemic world, you want to do everything you can to keep your body fit to fight viruses.


Water could be called the fourth macronutrient. It makes up around half of your body weight and is required for all your organ systems to function. The many health benefits of drinking water affect every system in your body–from the cardiovascular to the reproductive.

The consequences of even mild dehydration can lead to serious health conditions. Fortunately, our bodies have very good thirst mechanisms. As long as you follow your body’s cues, it’s not complicated to stay hydrated.

Frequently Asked Questions

Should I worry about drinking too much water?

Hyponatremia is an extremely rare serious condition in which your body gets over-hydrated. When you consume too much water, your sodium levels decrease, making your body unable to perform basic functions. It’s rare, but it is life-threatening when it happens. We usually only see it in endurance athletes (such as marathon runners), who sometimes drink excess water to avoid getting dehydrated during intense or prolonged exercise. Outside of this context, consuming enough fluids to cause hyponatremia is challenging. Not drinking enough water is a much more common problem.

What liquids count towards your daily water goal?

Nearly all liquids count toward fluid intake. That includes caffeinated and sugary drinks, but your healthiest and most affordable choice is always pure water. One last thing to remember is that about 20% of your daily water intake comes from your food. The more fresh, moist foods you eat, the less you must drink water during the day. In addition, people who are malnourished and drink a lot of beer (beer potomania) and other malnourished people (such as those with a low-protein, high-water diet, or “tea and toast syndrome”) may have a marked decrease in their ability to get rid of water. This is directly caused by their poor diet.

What about caffeine? How does it affect water intake and hydration?

For decades, people thought consuming caffeinated drinks such as coffee caused the body to lose water. Caffeine is a diuretic, which means it can cause excessive urination by inhibiting the body’s fluid regulation system’s ability to function properly. Recent studies showed that despite this, even caffeinated drinks usually increase total hydration due to the amount of water in them. Besides, regular coffee drinkers develop a tolerance[20] to the diuretic effect. And the diuretic effect isn’t noticeable at low doses[21]. While we don’t advise living solely on coffee or other caffeinated beverages, your morning cup (or two) will still contribute to your hydration.

Do vegetables and fruits have to be fresh to help?

The gluteus muscles should be targeted if you want to get wider hips.Nope! Frozen, fresh, or cooked fruits and vegetables are all water-rich foods. Be careful with canned food, which can be high in sodium.

+ 21 sources

MIDSS adheres to strict procurement guidelines and relies on peer-reviewed studies, academic research institutes, and medical associations. We work mainly with peer-reviewed studies to ensure the accuracy of the information. We avoid the use of tertiary references. You can read about how we ensure the accuracy and timeliness of our content in our editorial process.

  1. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. (2005). [online] Washington, D.C.: National Academies Press. doi:10.17226/10925.
  2. NHS Choices (2023). Dehydration. [online] Available at: [Accessed 8 Feb. 2023].
  3. (2013). How to calculate how much water you should drink | University of Missouri System. [online] Available at: [Accessed 5 Jan. 2023].
  4. Anon, (2023). Products – Data Briefs – Number 242 – April 2016. [online] Available at:,)%20for%20women%20(2). [Accessed 5 Jan. 2023].
  5. Martin, C., Ling, P.-R. and Blackburn, G. (2016). Review of Infant Feeding: Key Features of Breast Milk and Infant Formula. Nutrients, [online] 8(5), p.279. doi:10.3390/nu8050279.
  6. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. (2005). [online] Washington, D.C.: National Academies Press. doi:10.17226/10925.
  7. The Texas Heart Institute. (2018). If salt keeps water in the body, why do salt tablets make dehydration worse? | Texas Heart Institute. [online] Available at: [Accessed 5 Jan. 2023].
  8. ROBERTS, K.E. (1963). Mechanism of Dehydration Following Alcohol Ingestion. Archives of Internal Medicine, [online] 112(2), p.154. doi:10.1001/archinte.1963.03860020052002.
  9. CDC (2020). The Role of Sodium in Your Food. [online] Centers for Disease Control and Prevention. Available at:,don’t%20even%20taste%20salty [Accessed 5 Jan. 2023].
  10. Lopez, R.M., Lund, D.C., Tritsch, A.J. and Liebl, V. (2022). Relationship Between Pre- and Post-exercise Body Mass Changes and Pre-exercise Urine Color in Female Athletes. Frontiers in Sports and Active Living, [online] 4. doi:10.3389/fspor.2022.791699.
  11. NHLBI, NIH. (2022). Staying hydrated throughout life may reduce the risk of heart failure. [online] Available at:,-March%2031%2C%202022&text=Staying%20well%2Dhydrated%20may%20be,of%20Cardiology%20Congress%20in%202021. [Accessed 5 Jan. 2023].
  12. Zhang, N., Du, S.M., Zhang, J.F. and Ma, G.S. (2019). Effects of Dehydration and Rehydration on Cognitive Performance and Mood among Male College Students in Cangzhou, China: A Self-Controlled Trial. International Journal of Environmental Research and Public Health, [online] 16(11), p.1891. doi:10.3390/ijerph16111891.
  13. EMBON, O.M., ROSE, G.A. and ROSENBAUM, T. (1990). Chronic Dehydration Stone Disease. British Journal of Urology, [online] 66(4), pp.357–362. doi:10.1111/j.1464-410x.1990.tb14954.x.
  14. (2021). [online] Available at:,eat%20less%2C%20promoting%20weight%20loss. [Accessed 5 Jan. 2023].
  15. Orthopedic Associates (2020). Dehydration and Joint Pain: How Your Hydration is Affecting Joint Health – Orthopedic Associates. [online] Orthopedic Associates. Available at:’s%20estimated%20that%2070%20%E2%80%93%2080,feet%2C%20shoulders%2C%20and%20hands. [Accessed 5 Jan. 2023].
  16. Boschmann, M., Steiniger, J., Hille, U., Tank, J., Adams, F., Sharma, A.M., Klaus, S., Luft, F.C. and Jordan, J. (2003). Water-Induced Thermogenesis. The Journal of Clinical Endocrinology & Metabolism, [online] 88(12), pp.6015–6019. doi:10.1210/jc.2003-030780.
  17. Franciscan Health. (2022). Hydration Helps Your Health. [online] Available at:,energy%20and%20helps%20fight%20fatigue. [Accessed 5 Jan. 2023].
  18. Sawka, M., Latzka, W., Matott, R. and Montain, S. (1998). Hydration Effects on Temperature Regulation. International Journal of Sports Medicine, [online] 19(S 2), pp.S108–S110. doi:10.1055/s-2007-971971.
  19. Armstrong, L.E., Ganio, M.S., Casa, D.J., Lee, E.C., McDermott, B.P., Klau, J.F., Jimenez, L., Le Bellego, L., Chevillotte, E. and Lieberman, H.R. (2011). Mild Dehydration Affects Mood in Healthy Young Women. The Journal of Nutrition, [online] 142(2), pp.382–388. doi:10.3945/jn.111.142000.
  20. Maughan, R.J. and Griffin, J. (2003). Caffeine ingestion and fluid balance: a review. Journal of Human Nutrition and Dietetics, [online] 16(6), pp.411–420. doi:10.1046/j.1365-277x.2003.00477.x.
  21. Seal, A.D., Bardis, C.N., Gavrieli, A., Grigorakis, P., Adams, J.D., Arnaoutis, G., Yannakoulia, M. and Kavouras, S.A. (2017). Coffee with High but Not Low Caffeine Content Augments Fluid and Electrolyte Excretion at Rest. Frontiers in Nutrition, [online] 4. doi:10.3389/fnut.2017.00040.


Nia is a STEM educator, certified personal trainer, fitness instructor, and certified nurses' aid. She received her Bachelor's in Creative Writing and Music Theory from The College of Idaho in 2010 at the age of 18. She spent the next 5 years studying Biochemistry and STEM education at Boise State University. Now a mother of 2, she resides in central Idaho and owns a writing agency specializing in content and copywriting for Health, Science, & Education.


Elizabeth Gonzalez Cueto, MD
Medical Doctor & Medical Writer
My name is Elizabeth and I am a Medical Doctor (MBBS) with experience as a medical and research article writer, reviewer and proofreader. I have worked for the American Journal of Case Reports, the Medical Science Monitor, and Pacific Medical Training as a medical article reviewer and writer. Besides, I have worked as a medical interpreter and translator for Angel City research and SC3 Research group as a medical research assistant for several clinical trials. My academic background includes many international scientific environments like Oxford University, United Kingdom. Hannover Medical School, the University of Tours, France. the Autonomous University of Barcelona and the National Polytechnic Institute in Mexico.

Help us rate this article

Thank you for your feedback

Keep in touch to see our improvement