How much water do you actually need?
A bodyweight-based target that adjusts for exercise and climate — not a magic 8-glass rule.
Your details
Climate
Typical indoor climate
Your glass / vessel size
Daily water intake
≈ 2,700 ml
How that looks in common vessels
This includes water from food (about 20% of daily intake on a typical diet). Drink to thirst — a steady, pale-yellow urine colour is the simplest hydration check.
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Frequently asked questions
How much water should I drink a day?+
A practical baseline is about 35 ml per kg of bodyweight — roughly 2.4 L for a 70 kg adult. Add 500 ml per hour of exercise, and another 250–500 ml in warm or hot conditions. Food contributes about 20% of your daily water intake.
Is the '8 glasses a day' rule true?+
It's a rough approximation, not science. Needs vary with body size, activity, climate, age and diet. Our calculator personalises the number using bodyweight and activity, which is much more accurate.
How do I know if I'm hydrated?+
The simplest check is urine colour — pale straw indicates good hydration; dark yellow means drink more. Drinking to thirst works for most healthy adults; older people and athletes should drink proactively.
Can you drink too much water?+
Yes, but it's rare. Hyponatraemia (dilutional low sodium) can occur from very large volumes (over 5 L) in short periods, especially during endurance exercise. Spread intake across the day and include electrolytes for long or intense workouts.