Daily water intake calculator: optimal hydration
Water is the most essential nutrient. Adequate hydration regulates body temperature, transports nutrients, and facilitates cognitive functions. The calculator estimates your daily needs based on weight, activity, and climate.
How much water do you need per day?
The general recommendation is 35 ml per kg of body weight. A 70 kg person needs approximately 2.45 liters. Intense exercise adds 500–1,000 ml per hour, and hot days also increase the need.
Signs of dehydration
- Dark or concentrated urine (the most reliable indicator).
- Fatigue, headaches, and difficulty concentrating.
- Dizziness when standing up quickly.
- Dry mouth and cracked lips.
The 8-glasses-a-day myth
The 8-glasses recommendation has no universal scientific basis. Real needs vary by body size, activity, and diet. Water-rich foods (fruits, vegetables) also count toward total hydration.