Daily water needs by weight and activity.
These calculators use established formulas (such as Mifflin-St Jeor for calorie needs or the Devine formula for ideal weight) to provide general estimates. They're built for a general population and don't account for individual medical conditions, medications, or circumstances. They aren't a substitute for advice from a doctor, registered dietitian, or other qualified healthcare provider — especially for anything related to pregnancy, chronic conditions, or medication dosing.
Rough rule: 35 ml per kg of body weight per day, plus ~12 ml per minute of exercise. Total needs include water from food and other drinks.
Hot climate, altitude, breastfeeding, or fever raise needs. Pale-yellow urine is a better indicator than any formula.
Roughly 20% of daily water intake typically comes from food rather than drinks, especially from fruits, vegetables, and soups — this estimate covers total fluid need, not just what you need to drink separately.
70 kg person + 30 min exercise: 70 × 35 + 30 × 12 = 2,810 ml/day (~2.8 L, ~12 cups).
Rough baseline for average adults; underestimates for active or heavier people. Body-weight estimates are more personalized.
Yes — despite mild diuretic effect, coffee and tea net-hydrate.
Rarely, but extreme overhydration can cause hyponatremia. Usually only at multiple liters per hour.
Yes — increased sweat losses in heat or at altitude can push needs up significantly beyond the baseline estimate, sometimes by a liter or more depending on exertion and conditions.