Water Intake
Calculate daily water intake needs
These calculators provide general information only and are not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
How to use Water Intake
- 1Enter your body weight and choose kilograms or pounds.
- 2Fill in how long and how hard you train, since sweat losses raise requirements substantially.
- 3If you are in heat or at altitude, tick those options to account for the extra loss.
How daily water needs are estimated
Base need = weight (kg) × 30–35 ml; exercise = training minutes × extra factorThe most common rule is body weight times 30 to 35 millilitres, so a 60 kg person needs roughly 1.8 to 2.1 litres a day. That coefficient comes from measured daily losses through urine, breathing, skin evaporation and stool. For exercise, add roughly 350 to 700 ml per hour depending on intensity and how much you sweat.
One widespread misunderstanding deserves clearing up: the famous eight glasses, about two litres, is a memorable approximation that ignores weight, climate and activity. Just as importantly, that total does not all have to come from drinking, because food, especially fruit, vegetables and soups, supplies 20% to 30% of daily water, and metabolism generates around 300 ml. That means plain drinking water usually accounts for 500 to 800 ml less than the headline total. The simplest check is urine colour: pale straw means you are well hydrated, dark amber means drink more.
| Weight | Sedentary | Moderately active | Hard training 1h+ |
|---|---|---|---|
| 50 kg | ≈ 1.5–1.8 L | ≈ 1.8–2.0 L | ≈ 2.3–2.5 L |
| 70 kg | ≈ 2.1–2.5 L | ≈ 2.5–2.8 L | ≈ 3.0–3.2 L |
| 90 kg | ≈ 2.7–3.2 L | ≈ 3.2–3.5 L | ≈ 3.7–4.0 L |
Daily water suggestions by weight and activity
Frequently asked questions
Do coffee and tea count towards hydration?
Yes. Caffeine has a mild diuretic effect, but at normal intakes the net effect is still hydrating, and research generally counts coffee and tea towards daily fluid intake. What deserves attention are sugary drinks and alcohol: the first add calories, and the second is clearly diuretic and increases fluid loss.
If I feel thirsty, am I already dehydrated?
Not necessarily. Thirst is a reliable signal for most healthy adults and typically kicks in at about 1% to 2% fluid loss, a level that does not harm performance or health. Thirst does blunt with age, however, and children often forget to drink when absorbed in play, so both groups benefit from drinking on a schedule rather than waiting.
Is more water always better?
No. The kidneys can excrete only about 800 to 1,000 ml per hour, so drinking very large volumes quickly can cause hyponatraemia, with headache, nausea and confusion, and in extreme cases it is life threatening. It is most often seen after endurance events when people replace sweat with plain water and no electrolytes. Drinking steadily to thirst is enough for everyday life.
Do I need a sports drink when exercising?
It depends on duration and intensity. Up to about 60 minutes of easy to moderate work, water suffices. Beyond 60 to 90 minutes, or when you sweat heavily, a drink with sodium, around 300 to 600 mg per litre, and 4% to 8% carbohydrate helps maintain electrolyte balance and glycogen. Weighing yourself before and after gives a practical target: replace roughly 1.2 to 1.5 litres for every kilogram lost.