Water requirement calculator
Calculate your optimal water intake based on body weight and activity level. Rule of thumb: 35 ml per kg of body weight.
Note: This calculation is only a rough estimate and does not replace individual advice.
How does the calculator work?
- Enter your body weight in kilograms
- Select your activity level (low, moderate, or high)
- Your daily water requirement is instantly displayed in liters
- The number of glasses (250 ml) is automatically calculated
The calculation is based on 35 ml per kg of body weight, adjusted for your activity level.
How much water should I drink daily?
The recommendation is about 35 ml per kg of body weight. For a 70 kg person, that is approximately 2.5 liters daily. During exercise or heat, the requirement increases.
Why is water requirement higher with activity?
Through sweating, the body loses fluid. With moderate activity, the requirement increases by about 20%, with high activity by up to 40%.
Do coffee and tea count towards water intake?
Yes, coffee and tea contribute to fluid intake. The dehydrating effect of caffeine is minimal. However, most of your intake should still come from water.
How do I know if I am drinking enough?
The simplest indicator is urine color: light to slightly yellow means good hydration, dark yellow indicates fluid deficiency.
Can I drink too much water?
Yes, overhydration (hyponatremia) is possible but rare. Drink evenly throughout the day rather than large amounts at once.
When should I drink more than calculated?
During heat, fever, diarrhea, vomiting, or intense exercise. Requirements are also increased during pregnancy and breastfeeding.
How is the data calculated?
The calculator estimates your daily water requirement based on your weight and an activity factor. As a guideline, about 35 ml of water per kilogram of body weight is used. Depending on activity level this value is multiplied by a factor:
Water need (L) = weight (kg) × 0.035 × activity factor
| Activity | Factor |
|---|---|
| Low activity | 1.0 |
| Moderate activity | 1.2 |
| High activity | 1.4 |
What studies is the calculation based on?
- EFSA Guidelines on Water Intake (2010)
Key point: Recommends about 2–2.5 L of water per day for adults depending on activity, climate and individual needs.
Source: EFSA Journal 2010;8(3):1459 - Institute of Medicine (2004)
Key point: Recommends about 3.7 L for men and 2.7 L for women of total water per day (including beverages and food).
Source: National Academies Press
The formula provides approximate values. Individual factors such as climate, diet, health status or certain medications can influence water needs. If unsure, consult medical professionals.