How Much Water Your Body Needs Per Day When Exercising

Written by Tihomir Stefanov, M.S.(C), PT

| Published on

Fact Checked

We often hear the advice “Stay hydrated”, but odds are that most of you don’t know things about water, such as:

  • How much water to drink daily
  • How much water is too much
  • Hydration during workouts

Thing is, water is transparent and has no actual caloric value, meaning that it doesn’t really matter how much we take in… Right?

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Not really.

Water is the most common substance in our bodies, followed by protein.

What this simply means is that water is a key element in the regulation of many processes in the body.

Well, quite frankly, there isn’t really one ultimate answer that applies to each and everyone.
That is mainly because water intake, even though of no caloric value, is still like food – It varies from person to person.
For this article, we will give you valuable information and practical tips, to help you determine your optimal water intake.

What does water do in the body?

Water is one of if not the most vital substance for the body, period.

If someone talks against the importance of water intake, STOP listening to them – They are ignorant!

As we previously mentioned, water is of no caloric value.

However, macronutrients are just a part of the whole nutrition game, meaning that water is just as important.

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Before we tell you about the functions of water, let’s take a look at some facts:


  • ~70% of the body is made up of water
  • The percentage depends and varies in accordance with the body composition- Muscle is 75% water, fat is 25% water, bones and blood are 20% and 85% respectively

What this means is that if we take as an example two 200 lbs males, one with more fat and less muscle and the second with more muscle and less fat, well, then the body of the second male will contain more water.

That is because his body composition is primarily built of lean muscle, which contains 50% more water, as opposed to the predominant fat tissue in the first individual.

Therefore, the active trainee who has more lean muscle mass, will require more water to maintain their water balance.

Physiological functions of water

water functions in the body

  • Transports nutrients to cells
  • Cell cleanse from byproducts of different physiological processes
  • Joint lubrication
  • Thermal regulation
  • Source of minerals (if the water is good)

Water balance

Alright, if the body is 73% water, why drink water anyways?

To maintain those 73%, DUH!

Maintaining proper fluid balance in the body is important, if you want to feel healthy and physically capable.

We lose water in many processes – Urinating, breathing, sweating.

For the most part, a healthy adult loses about half a gallon of water daily, via the above-mentioned processes.

That loss however varies, according to certain factors, such as:

  • Levels of physical activity
  • Altitude
  • Alcohol consumption
  • Weather conditions


Well, most people drink water only once they are thirsty, which is actually a mistake, as thirst is the first sign of dehydration.

If you’re really thirsty, rest assured you’ve lost a substantial amount of bodily fluids.

Dehydration in its truest form occurs when the loss of fluids is greater than the intake of such.

There are many things that can lead to dehydration, including but not limited to:

  • Heavy sweating
  • Diarrhea
  • Vomiting

The bad thing about dehydration is not only that we lose a substantial amount of fluids, but it also interferes with the electrolyte balance of the body.

Symptoms of dehydration

symptoms of dehydration

Normally, people don’t really pay attention to their water intake.

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If you’re experiencing some of the following, you may be dehydrated:

  • Constipation and diarrhea
  • Light headedness
  • Prominent exhaustion
  • Frequent muscle cramps

These usually occur when we lose about 10% of our fluids.

Note – The body CANNOT ADAPT to dehydration! Losing more than 10% of your fluids will ultimately lead to serious physiological disfunctioning.

And so…

How much water do you need?

As mentioned, that really varies from person to person, but one thing we can say for sure – Do not wait to get thirsty!

On top of the fact no one takes care of their water intake, modern-day diets are deprived of foods rich in water.

That is to say you should look at the foods you’re eating too, because they are also a source of water, especially the veggies!

However, when it comes to water consumption in its purest form, we’d advise you to start off with a baseline 2.5 liters and move up from there, as you experiment and observe your body.

Once you reach a point where the daily amount of water feels good and not bloating, that is your optimal intake.

And then again, if the weather is too hot for example, or you are very active, you might need more fluids.

Just listen to your body!

Best sources of fluids

Here are our favorite sources, abundant of quality water:

  • Tea
  • Soups
  • Mineral and spring water
  • Fruits and veggies

How much water should you drink based on your weight?

Though highly individual, there are certain calculations for your approximate needs.

Those are basically about 30-40 ml. of water per kilogram of bodyweight (~15 ml per lbs.)

And so, if you are 70 kg, you would need about 3 liters of water DAILY.

Note – If your nutrition contains quality foods of good diversity, you’re generally going to take in about half a liter to one liter from food alone.

What this means is that if you calculate your water intake given the numbers above, you will have to take out 500 ml ~ 1 liter from the number, to calculate how much pure water you should drink.

And so, if you are 70 kg and need 3 liters, you should get 2.5 out of those 3 liters from drinkable water, while the rest will be granted by food.

Should I drink during training?

water intake during training

Physical activity, especially during the summer, increases the water demand of our bodies.

That is simply because, as I said, the weather conditions and the levels of physical activity are the main water-depleting factors.

Drinking water before, during and after a workout is important.

As a matter of fact, water intake should be consistent throughout the whole day, as you don’t want to compensate for the lack of intake earlier, with loads of water later on in the day.

Here are some practical tips:

  • Consume 500-700 ml of water gradually, during the hour prior to a workout – In doing so, you will do a water load and the thirst during the workout won’t be as prominent.
  • Drink less during the workout – It is possible that you feel your mouth is drying out during the workout. However, avoid chugging loads of water if that happens, as that will only make you feel bloated. Instead, have a couple of sips to just moisten up the mouth.
  • Breathe through the nose! – Breathing through the mouth is one of the first signs of exhaustion. Try this for once – Go through a whole workout with your mouth closed. Not only will that supercharge your workout, but it will also help you avoid having your mouth dry out.

Bottom line

Optimal daily water intake is not a constant and is individually determined, based on many factors.

We ultimately advise you to experiment and see how you feel with different amounts of water per day.

Also, try decreasing other fluids like coffee and alcohol, which deprive your body of fluids.

Last but not least, always try and have a bottle of mineral/spring water with you and NEVER reach excessive thirst!

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