How Much Water Should You Drink Per Day?
The question of the right water intake concerns many people. The German Nutrition Society (DGE) has a clear recommendation: 35 milliliters per kilogram of body weight per day. For a 75 kg adult, that's about 2.6 liters daily.
But this number is just a starting point. Your actual need depends on numerous individual factors -- from physical activity to climate to special circumstances like pregnancy or nursing.
The Scientific Basis: Why 35ml Per Kg?
The DGE guideline is based on the water loss our body experiences daily through various routes. We lose about 1.5 liters through urine, about 0.5 liters through breathing, 0.5 liters through the skin, and about 0.1 liters through stool. That totals approximately 2.6 liters for an average adult.
The European Food Safety Authority (EFSA) recommends 2.0 liters for women and 2.5 liters for men -- notably as total fluid intake including food.
Factor 1: Body Weight
Body weight is the most important factor. A larger body has more cells that need to be supplied with water. The 35ml-per-kg formula scales automatically:
- 50 kg: approx. 1.75 liters
- 65 kg: approx. 2.3 liters
- 80 kg: approx. 2.8 liters
- 100 kg: approx. 3.5 liters
Factor 2: Physical Activity
Exercise and movement significantly increase water needs. Through sweating, the body loses between 0.5 and 2 liters per hour depending on intensity and duration. With moderate exercise (2-3 times per week), you should drink about 500 ml extra; with daily exercise about 1 liter more; and with competitive sports up to 1.5 liters extra.
Important: Don't wait until you're thirsty. Thirst is already a sign of an emerging deficit. Ideally drink 150-200 ml every 15-20 minutes during exercise.
Factor 3: Climate and Temperature
High temperatures and low humidity significantly increase fluid loss. In summer or in heated rooms, more water evaporates through the skin:
- Normal temperatures (18-22 degrees C): no extra needed
- Warm weather (25-32 degrees C): about 400 ml more
- Extreme heat (over 32 degrees C): 800 ml or more extra
Dry heating air in winter can also increase needs -- so pay attention to adequate fluid intake even in the cold season.
Factor 4: Pregnancy and Nursing
Pregnant women need about 300 ml more water per day. The additional blood volume, amniotic fluid formation, and increased metabolism explain the extra need.
Nursing mothers need up to 700 ml more daily. Breast milk is about 87% water -- with daily milk production of 750-800 ml, the high additional need is almost self-explanatory.
Factor 5: Coffee and Caffeinated Drinks
Contrary to popular belief, coffee does not dehydrate the body. Studies show that the fluid content of coffee far exceeds the diuretic effect of caffeine. Nevertheless, we recommend planning about 150 ml extra per cup of coffee, as the mild diuretic effect slightly reduces the net contribution to hydration.
Factor 6: Alcohol
Unlike coffee, alcohol has a much stronger diuretic effect. Alcohol inhibits the antidiuretic hormone (ADH), leading to increased urine production. With 1-2 drinks, you should drink about 350 ml more water; with 3 or more drinks, even 750 ml extra.
The 20% Rule: Water From Food
About 20% of your daily water needs are covered by solid food. Particularly water-rich foods include:
- Cucumber: 96% water
- Watermelon: 92% water
- Tomatoes: 95% water
- Lettuce: 95% water
- Strawberries: 91% water
- Zucchini: 95% water
A balanced diet rich in fruits and vegetables significantly contributes to fluid supply.
Practical Everyday Tips
1. **Morning ritual:** Drink a large glass of water (300-500 ml) right after waking up. Your body has lost fluid overnight.
2. **Water bottle companion:** Always have a filled water bottle with you -- at work, in the car, during sports.
3. **Hourly reminder:** Set a timer or use a drinking app as a reminder.
4. **Before meals:** A glass of water before eating aids digestion and can help with weight loss.
5. **Variety:** Flavor your water with lemon, cucumber, mint or ginger if plain water is too boring.
6. **Urine check:** Light yellow to clear urine indicates good hydration. Dark urine signals you should drink more.
Conclusion: Your Individual Water Needs
There is no universal answer to how much water you should drink. Your personal needs depend on body weight, activity, climate and lifestyle. Use our water intake calculator to determine your individual needs -- and distribute the amount evenly throughout the day.