Water Intake Calculator
Find out exactly how much water you should drink each day. Based on your body weight, exercise, climate, and special conditions. See your target in liters, ounces, glasses, and a daily schedule.
Your daily water target
How much water should you drink?
The European Food Safety Authority recommends about 2.5 liters per day for men and 2.0 liters for women, including water from food (which provides about 20-30% of total intake). The US National Academies recommends 3.7 liters for men and 2.7 liters for women from all beverages and foods.
Factors that increase your water needs
Exercise: Add ~350ml for every 30 minutes of activity. Hot/humid climate: Add ~500ml for sweating. High altitude: Add ~500ml due to increased respiration and drier air. Pregnancy: Add ~300ml. Breastfeeding: Add ~700ml.
Signs you need more water
Dark yellow urine, headache, fatigue, dizziness, dry mouth, and reduced urine output are common dehydration signs. Aim for pale yellow or clear urine. If you feel thirsty, you're already mildly dehydrated — sip water throughout the day rather than drinking large amounts at once.
Related: BMR Calculator · Calorie Calculator · BMI Calculator
· Reviewed by the Vital Health Editorial Team
How This Calculator Works
This calculator estimates daily water needs based on body weight, activity level, and climate. The baseline reference comes from the U.S. National Academies of Sciences, Engineering, and Medicine: approximately 3.7 liters (125 oz) per day for men and 2.7 liters (91 oz) per day for women from all beverages and foods. About 20% of daily fluid intake comes from food. The calculator adjusts the baseline for body weight, exercise duration, and hot/dry climates.
For informational purposes only — not medical advice. Individual hydration needs vary based on health conditions, medications, and activity level.
Frequently Asked Questions
Do I really need 8 glasses of water a day?
The '8 glasses a day' rule is a myth with no scientific basis. The National Academies recommends 3.7L (men) and 2.7L (women) from ALL fluids and foods combined — about 20% comes from food. You may need more if you exercise, live in a hot climate, or are pregnant/breastfeeding. Drink when thirsty; your urine should be pale yellow.
Does coffee and tea count toward daily water intake?
Yes. While caffeine is a mild diuretic, the net fluid contribution of coffee and tea is positive. A 2014 study found that moderate coffee intake (3–4 cups) hydrates similarly to water. However, water is still the healthiest choice as it contains no calories, sugar, or additives.
Can you drink too much water?
Yes. Overhydration (hyponatremia) occurs when you drink so much water that sodium levels in your blood become dangerously diluted. This is rare but can occur during endurance events (e.g., marathons) when athletes drink excessive water without replacing electrolytes. Symptoms include nausea, headache, confusion, and in severe cases, seizures.
Sources & References
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