Calculators
Water Intake Calculator
Estimate how much water to drink each day from your weight, activity level, and climate, shown in litres and glasses.
about 11 glasses (250 ml) or 2810 ml
Individual needs vary with health, medication, and conditions. Spread intake through the day, and drink more during exercise or heat. Consult a doctor for personal advice.
How it works
A common starting point is about 33 ml of water per kilogram of body weight. Activity and a warm climate raise the figure because you lose more fluid through sweat and breathing.
Litres = weight (kg) × 0.033 + activity bonus + climate bonusPregnancy and breastfeeding add to the total. The result is a daily target to spread across the day, not an amount to drink in one go.
Intake by weight and activity
Daily targets in a temperate climate. Warm or hot weather adds roughly 0.3 to 0.7 litres on top.
| Weight | Sedentary | Moderate | Active |
|---|---|---|---|
| 50 kg | 1.7 L | 2.2 L | 2.4 L |
| 70 kg | 2.3 L | 2.8 L | 3.1 L |
| 90 kg | 3.0 L | 3.5 L | 3.7 L |
Frequently asked questions
Can you drink too much water?
Yes, though it is rare. Drinking far more than you need in a short time can dilute blood sodium, which is dangerous. Spread your intake through the day rather than forcing large amounts at once.
Do coffee and tea count?
Mostly yes. Despite a mild diuretic effect, the fluid in coffee, tea, and most drinks still contributes to hydration. Water and unsweetened drinks are the best choices.
How much extra should I drink when exercising?
Add roughly 0.5 to 1 litre for every hour of exercise, and more in heat. Drink before, during, and after activity rather than all at once afterward.
Does food count toward hydration?
Yes. Foods with high water content such as fruit, vegetables, and soup can supply a meaningful share of daily fluid, which is one reason needs vary between people.
Is the eight glasses a day rule accurate?
It is a rough guide, not a rule. Real needs depend on body size, activity, climate, and health, which is why this tool bases the estimate on your weight and lifestyle.