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How Much Water Should You Drink a Day and Why?

It's no secret that water is the most important nutrient for the human body, and we need to consume it every day.

Of course, this brings about the question, how much water should you drink? The amount of water we need to drink varies depending on our age, gender, physical activity level, and climate. 

The very general recommendation for adults is you need half your body weight in pounds, in ounces of water. So if you weigh 130 pounds, you'll aim to drink about 65 ounces or 8 ½ cups of water per day.

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Does this seem like a lot? Perhaps you've heard that you should be drinking at least 8 glasses of water per day. For many, this is a daunting figure. However, it's actually not as difficult as it sounds.

Remember, all fluids count towards your daily water intake, not just water. While we want water to be our main source of hydration, things like juices, teas, coffee, and even some foods, like watermelon contribute to our daily fluid needs.

In general, you should drink water throughout the day, starting first thing in the morning, especially before, during, and after physical activity.

If you are sweating a lot or are in a hot climate, you will need to drink even more water to stay hydrated.

Dehydration severely impacts athletic performance and can lead to a number of health problems, such as headaches, fatigue, and dizziness.

It is important to drink enough water each day to avoid these problems. Let's look at more reasons why water is so important for our health.

Why Water is Important For Your Health 

Water is essential for the human body and makes up a large percentage of our body weight. In fact, water makes up about 60% of our body weight. Every system in our body needs water to function properly (6). For example, water:

  • Lubricates our joints
  • Regulates our body temperature
  • Cushions our organs
  • Flushes out toxins
  • Carries nutrients and oxygen to our cells

Water is essential for our survival. We need to make sure we are getting enough water each day to stay healthy and hydrated.

What Affects Water Needs?

Age: Babies and young children need more fluids than adults do in proportion to their body weight.

Body composition: Those who have a higher body weight generally require more fluids. 

Pregnancy and breastfeeding: Women who are pregnant or breastfeeding need more fluids than women who are not.

Physical Activity: People who are physically active need more fluids than people who are not.

Climate: People who live in hot, humid, or high-elevation climates will require more fluids than people who live in cooler climates.

Diet: People who eat a lot of salt or who eat a lot of high-fiber foods may have increased thirst and need more fluids than people who do not (10).

Medical conditions: People with certain medical conditions, such as kidney disease or heart disease, may need to adjust or limit their fluid intake.

In general, the more active you are and the hotter the climate you live in, the more water you need to drink. 

Athlete Fluid and Water Considerations

If you're an athlete, you need to be especially careful to stay hydrated, not just for your safety but for your performance. Your resting heart rate is significantly higher when dehydrated (14).

Fluid needs will vary significantly based on sport, intensity, climate, duration, and sweat rate.

A good rule of thumb is to drink about 4 oz of fluid every 15 minutes during training and to replenish with 16 oz of fluid for every pound lost during exercise. You can measure this by weighing yourself pre and post-workout, match, race, etc. Base sweat rate will vary significantly from person to person but generally averages between 1-4 lbs/hr. Those who maintain a higher weight will usually have a higher sweat rate (13). 


If you're exercising in a hot climate, at high elevation, and/or at a high intensity, you will need to drink even more water to stay hydrated.

It's also important to drink before, during, and after your workout, even if you don't feel thirsty. During intense workouts, gastric emptying is delayed, which may reduce how thirsty you feel and how quickly you are able to absorb fluids.

When sweating in high amounts, electrolyte repletion is also essential to avoid hyponatremia (low blood sodium levels) by only replacing water.  The main electrolytes lost in sweat include salt (sodium and chloride), potassium, magnesium, and calcium. The most noticeable effect of electrolyte loss will be muscle cramping, but you may also experience fatigue and decreased athletic and cognitive performance (11, 12).

What counts towards your water needs? 

All fluids count toward your daily hydration needs, but water is the best choice. Other options include (7):

  • Milk and plant-based milk substitutes
  • Fruit juice
  • Soda
  • Sports drinks
  • Coffee and tea
  • Broths
  • Hydrating foods: Watermelon, Cantaloupe, Lettuce, Celery, Yogurt, etc (15). 


While all fluids count towards fluid needs, drinking sugar-sweetened beverages adds calories without providing nutrition or satiety. Frequent consumption is associated with weight gain, obesity, type 2 diabetes, heart disease, kidney disease, non-alcoholic liver disease, dental issues, and gout (1,2,3).

If you noticed coffee and tea on this list and questioned it, yes, it’s correct. There's been much debate about whether coffee and tea are hydrating or dehydrating due to the diuretic effects of caffeine. Studies have shown that in order for caffeinated beverages to have a dehydrating effect, you would need to drink upwards of 500 mg of caffeine which equates to 4-5 cups of coffee (8, 9).

What Are the Signs of Dehydration?

It's important to drink enough water each day to avoid dehydration. Dehydration can lead to a number of health problems, such as headaches, fatigue, and dizziness. It can also make it more difficult to exercise and can lead to heat stroke.

Here are some signs that you may be dehydrated:

  • Thirst
  • Dry mouth
  • Lack of energy
  • Headache
  • Dizziness
  • Dark-colored urine

If you're experiencing any of these symptoms, it's important to drink more fluids and seek medical help if the symptoms are severe.

Health Benefits of Adequate Hydration 

Hydration can have a positive impact on several aspects of your health, including:

Preventing Chronic Disease: Proper hydration is essential for flushing toxins out of vital organs, maintaining proper kidney function, and preventing constipation (5, 6).

Regulating Body Temperature: Water helps to regulate your body temperature by sweating and respiration. It also helps insulate your body and protect your joints and organs.

Maximizing Performance: Adequate hydration is necessary for optimal physical performance. Dehydration can lead to fatigue, muscle cramps, and heat exhaustion. So if you're an athlete or just someone who spends a lot of time working out, it's important to make sure you're properly hydrated.

Helping Bodily Functions: Every system in your body needs water to function properly. Water helps carry nutrients to your cells and helps your body absorb them. It also helps to lubricate your joints, protect your spinal cord, and keep your skin healthy. The list goes on and on!

Supporting Digestion and Preventing Constipation: Water is necessary for proper digestion and prevents constipation. When you're properly hydrated, your body is able to break down food more efficiently and eliminate waste more effectively.

Supporting Your Mind: Dehydration can lead to headaches, difficulty concentrating, and mood swings. So if you're feeling irritable or having trouble focusing, make sure you're getting enough water (4).

Aiding in Weight Loss Efforts: Proper hydration is essential for proper metabolism and can help you lose weight (16). When you're properly hydrated, your body is able to burn calories more effectively. This is because of the fact that water helps your body to break down fat and use it for energy, and it also helps to keep you feeling full, so you're less likely to overeat.
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How to know if you're meeting your fluid needs

If you're not sure whether you're meeting your hydration needs, there are a few things you can look for.

Check your urine color—if you're adequately hydrated, your urine should be between colorless and light yellow.  If it's completely transparent, you may be over-hydrated, and if it's dark yellow or amber, you're likely dehydrated. 

Check your thirst—if you're thirsty, that's a sign that you're already dehydrated. In fact, once you're already thirsty, it's past the time when you should start drinking water.

Check your dry mouth—if your mouth feels dry or sticky, that's another sign that you're not getting enough fluids.

Check your fatigue—if you're feeling tired or sluggish, that could be a sign of dehydration.

Check your head—if you're feeling lightheaded or dizzy, that's also a sign that you're not getting enough fluids.