Water Intake Calculator
Daily water intake from body weight (about 30–35 ml per kg) plus extra for exercise and heat. An estimate — thirst, urine colour and activity are better guides than any single number.
Your daily water target
2.6–3.0 litres
That is about 10–12 glasses (250 ml each). Base need 2.1–2.5 L, plus 0.5 L for exercise and heat.
Thirst and urine colour are better guides than any single number — pale yellow urine means you are hydrated. Do not force huge volumes: drinking far beyond thirst can dilute blood sodium (hyponatraemia). Food also counts: roughly 20% of daily water normally comes from food.
Formula & source — 30–35 ml per kg — EFSA / Institute of Medicine guidance
Base intake = body weight (kg) × 30–35 ml. The European Food Safety Authority (EFSA, 2010) adequate intakes are 2.5 L/day for men and 2.0 L/day for women from all sources (food + drink); the U.S. Institute of Medicine (2005) figures are 3.7 L/day for men and 2.7 L/day for women. The 30–35 ml/kg rule reproduces those figures for typical body weights. Exercise adds ~0.5 L per 30 minutes (American College of Sports Medicine).
Estimate, not medical advice. FitCalc results are estimates based on population-average formulas. They are not a diagnosis, a prescription, or a substitute for professional medical advice. If you have a medical condition, are pregnant, or take medication, talk to a doctor or registered dietitian before changing your diet or exercise. FitCalc claims no medical credentials.
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