Water Intake Calculator
Proper hydration is essential for your body to function: it regulates body temperature, transports nutrients, eliminates toxins, and lubricates joints. The amount of water you need each day depends mainly on your body weight and how much exercise you do. This calculator applies the standard nutrition recommendation for healthy adults in temperate climates.
Recommended daily water
liters
In milliliters
Glasses of 250 ml
Based on 35 ml/kg plus 500 ml per hour of exercise (a common clinical rule of thumb). Excludes water contained in food.
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How it works
The formula applied is: daily water (ml) = weight (kg) × 35 + exercise hours × 500. The base factor of 35 ml per kilogram is a common clinical rule of thumb for adults under normal conditions. The extra 500 ml per hour of exercise compensates for additional losses through sweating. The result does not include water contained in food (which contributes approximately 500–700 ml additionally).
Recommended water by body weight
A widely used rule of thumb is to drink between 30 and 35 ml of water per kilogram of body weight per day, not counting exercise. The table converts that range into liters for the most common weights; add about 500 ml for every hour of intense physical activity. These are guideline values for healthy adults in a temperate climate: on hot days or with a fever, the needs rise.
| Body weight | Water per day (30–35 ml/kg) |
|---|---|
| 50 kg | 1.5 – 1.8 liters |
| 60 kg | 1.8 – 2.1 liters |
| 70 kg | 2.1 – 2.5 liters |
| 80 kg | 2.4 – 2.8 liters |
| 90 kg | 2.7 – 3.2 liters |
| 100 kg | 3.0 – 3.5 liters |
Factors that raise your needs and signs of dehydration
Several situations increase the daily requirement: exercise and heat through sweating, fever and infections, pregnancy (about 300 ml extra) and breastfeeding (up to 700 ml extra), and high altitude. High-protein or high-fiber diets also raise it. Watch for the signs of dehydration: intense thirst, dry mouth, dark and scanty urine, headache, dizziness, tiredness and reduced concentration.
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Preguntas frecuentes
- How much water should I drink per day?
- The general EFSA recommendation is 2 liters for women and 2.5 liters for men including water from food. In terms of water to drink, it is usually between 1.5 and 2.5 liters depending on weight and activity. This calculator gives you a personalized value based on your weight and exercise.
- Do coffee, tea, and herbal infusions count toward hydration?
- Yes. Despite the popular myth, coffee and tea have a moderate diuretic effect but contribute to the net fluid balance. Caffeinated beverages do not dehydrate as long as they are consumed in reasonable amounts (less than 400 mg of caffeine per day). Plain water is still the best option, but it is not the only one.
- How do I know if I am well hydrated?
- The most practical indicator is urine color: pale yellow (like lemonade) indicates good hydration; dark yellow or amber means you need to drink more water. Thirst is also a valid signal, although in older adults the thirst mechanism may be reduced.
- How much extra water do I need when exercising?
- During exercise you can lose between 0.5 and 2 liters per hour depending on intensity and temperature. The general recommendation is to drink 500 ml before exercise, between 150 and 250 ml every 15–20 minutes during exercise, and an additional 500 ml for each hour completed.
- Is it possible to drink too much water?
- Yes. Hyponatremia from excess water (water intoxication) is real, though rare under normal conditions. It mainly occurs in marathons and long endurance sports when excessive water is consumed without replenishing electrolytes. In daily life, healthy kidneys can handle up to 0.8–1 liter per hour without problems.