Omni Calculator logo

Water Intake Calculator

Created by Hanna Pamuła, PhD and Łucja Zaborowska, MD, PhD candidate
Reviewed by Bogna Szyk and Steven Wooding
Based on research by
National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate 2005.; The National Academies Press.; 2005See 1 more source
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement; Medicine & Science in Sports & Exercise; February 2007
Last updated: Jun 05, 2023

This water intake calculator will help you to estimate your adequate water intake per day. Whether you want to check daily water intake for an adult, teen, child, or even infant, this hydration calculator can do it in no time.

The values shown in our tool come from the Dietary Reference Intakes by the Institute of Medicine. Remember that those are only the rule-of-thumb values, and the actual amount you need may depend on many other factors than gender and age: lifestyle, body size, ambient temperature, climate, physical activity, metabolism rate, and general health condition.

Dehydration problem

Water is essential for life. It covers 71% of the planet's surface, and our bodies contain around 50-75% of that molecule (check our total body water calculator to find out yours); moreover, we can survive only a couple of days without water.

It has critical importance in health, and its deficit can cause serious problems. Don't let dehydration take you by surprise! The symptoms are:

  • Headache, stomachache;
  • General discomfort;
  • Reduced strength and athletic performance;
  • Loss of appetite;
  • Decreased urine volume, darker color;
  • Unexplained tiredness, confusion;
  • Purple fingernails; and even
  • Seizures.

How does the daily water intake calculator work?

Our calculator can help in determining the approximate amount of water you need to drink per day to prevent dehydration. It is based on the Adequate Intake (AI) measure, which is the median total water intake from U.S. survey data:

Age (years)

AI (milliliters/day)


0–6 mths


7–12 mths




























The values in the table are total water values, which include water from food and drink. Water and other beverages represent approximately 81% of total water intake, and the water contained in food provides the remaining 19%. It's easy to notice that daily AI for men and women is 3.7 L and 2.7 L per day, respectively. You may find all these values in our water intake calculator – it displays total water (from both food and drinks) and the amount you should consume in the form of beverages.

Minimum water requirement is sometimes calculated from your weight – simply divide your body weight (in pounds) by 2. For example, for a 180 lb person (~82 kg), the recommended water intake is 90 fl oz (2.7 L). If you want to check that rough estimation, you can use our weight converter to change between the units, and similarly, for the water volume, you may find helpful the volume converter tool.

The water intake calculator shows the standard values of adequate water intake, but it doesn't take into account physical activities or your lifestyle. Why? There are many factors that influence the proper fluid intake, mentioning only the intensity of the exercise, sweating rate, metabolic rate, weather conditions, and humidity.

In general, it is recommended to keep fluid intake between 17-25 oz (approx 500-750 ml) per hour of the exercise. It may vary according to your weight on the weather conditions in which you are training:

  • 16-18 oz (~475-530 ml) per hour of exercise for lighter weight athletes / exercising in cooler temperatures; and
  • Up to 28 oz (~830 ml) per hour of exercise for heavier athletes / exercising in hotter conditions.

According to the article Exercise and Fluid Replacement, the pre-hydration and drinking after excessive physical activity are also important issues:

  • At least four hours before the exercise, drink the beverages slowly (e.g., 5-7 mL per kilogram of body weight).

  • Drink during your workout. The hourly sweat losses are in the 0.5 to 2.0 L/h range for vigorous physical activity, so the water needs may vary.

  • Normal hydration state may be restored by standard meals and beverages. If you need a fast and complete recovery from excessive dehydration, you can drink ~1.5 L of fluid for each kilogram of body weight lost.

How much water should I drink?

The most important rule, which can't be put into any calculator – listen to the signs your body is giving. Whenever you are feeling thirsty – have a drink. Have a look at your urine color – the lighter it is, the more hydrated you are.

There are several conditions in which we should drink more – the most important is increased sweating (exercise, hot weather), but also several disease states like diarrhea or vomiting. Then you need to trust not only your thirst but also common sense.

Elderly adults and children experience thirst less intensely than adults, so ensure your child is drinking enough water, especially during summer and physical activities.

Can I drink too much water?

It's rare, but it's possible. Our kidneys can filter and excrete up to 15 liters of water every day, so it's really difficult.

Overhydration is called hyponatremia, and it usually comes from not too much water but rather from an imbalance between water and electrolytes. But don't worry too much; you’d have to drink gallons of water to suffer hyponatremia, especially drinking lots of fluids lacking the proper electrolyte profile.

Tap or bottled water?

You've calculated the adequate intake with our hydration calculator, and it turns out that you need to drink much more water than you expected. The next question arises, which one should you choose: tap or bottled water?

As in many countries, tap water is perfectly clean, healthy, and with good mineral content. We can recommend tap water, echoing many governments and environmental NGOs.

To check how much you can save rejecting bottled water, use our tap water calculator – you will be surprised by how cheap tap water is and how significant the potential savings are! But always remember to check for the quality and hardness regularly.

Hanna Pamuła, PhD and Łucja Zaborowska, MD, PhD candidate
Child or adult?
Male or female?
Total water (incl. water in food): ≈ 3.7 L/day
Water from beverages: 3.0 L (≈ 13 cups) /day

Adequate Intake based on Dietary Reference Intakes (Institute of Medicine 2005). Actual water requirements may vary according to the physical activity, climate, weather, health and other conditions.
Check out 21 similar electrolytes & fluids calculators 🧪
Acid-baseAnion gapArterial blood pH… 18 more
People also viewed…

Adderall dosage

The Adderall dosage calculator computes the proper dose of Adderall (amphetamine) for both narcolepsy and ADHD.

BODE index

The BODE Index calculator predicts survival in patients with Chronic Obstructive Pulmonary Disease (COPD).

Free fall

Our free fall calculator can find the velocity of a falling object and the height it drops from.


Do you feel like you could be doing something more productive or educational while on a bus? Or while cleaning the house? Well, why don't you dive into the rich world of podcasts! With this podcast calculator, we'll work out just how many great interviews or fascinating stories you can go through by reclaiming your 'dead time'!
Copyright by Omni Calculator sp. z o.o.
Privacy, Cookies & Terms of Service