Water Intake Calculator
This calculator estimates daily water needs using the widely used rule of about 35 ml per kilogram of body weight — consistent with the adult total-intake reference values published by the European Food Safety Authority (roughly 2.0 L for women and 2.5 L for men) — and adds about 350 ml for every 30 minutes of exercise. Keep in mind that food typically covers 20–30% of total fluid intake, and needs rise in hot weather, at altitude, during pregnancy or illness. This tool is for information only and is not medical advice.
Frequently asked questions
Is the "8 glasses a day" rule correct?
It is a rough simplification. Needs scale with body size and activity: 8 glasses of 240 ml is about 1.9 L, close to the estimate for a 55 kg adult, but too little for larger or very active people. A weight-based estimate is more useful.
Do coffee and tea count toward my water intake?
Yes. Despite the caffeine, coffee and tea contribute net fluid, as do milk, soups and water-rich foods such as fruit. Alcohol, on the other hand, promotes fluid loss.
Can I drink too much water?
Yes — drinking far beyond needs in a short time can dilute blood sodium (hyponatremia), which is rare but dangerous. Spread intake across the day and let thirst and urine color guide you; consult a doctor if you have kidney or heart conditions.