Water needs are surprisingly individual: body size, activity, climate and diet all shift the amount you should drink across a day.
This calculator uses a simple weight-based rule and adds extra for exercise time, then expresses the result in liters and everyday glasses so it is easy to act on.
For educational purposes only — not medical advice.
How to use
- Enter your body weight in kilograms.
- Add the minutes of exercise you do on a typical day, or leave it at zero.
- Press Compute to see your daily water target.
- Spread the total across the day instead of drinking it all at once.
- Add more in hot weather, during illness or when pregnant or breastfeeding.
Frequently asked questions
How much water should I drink a day?
A common working rule is about 35 ml per kilogram of body weight, which puts most adults between 2 and 3 liters a day before exercise is added.
How does exercise change my target?
We add roughly 350 ml for every 30 minutes of activity, since sweating is the main way you lose fluid during a workout.
Do coffee and tea count toward water intake?
Yes. The fluid in tea, coffee and other drinks contributes, and the mild diuretic effect of normal caffeine intake does not offset the volume you drink.
Can I drink too much water?
Rarely, but it is possible. Drinking several liters very quickly can dilute blood sodium to a dangerous level, so spread your intake through the day.
What are signs I am not drinking enough?
Dark yellow urine, headache, dry mouth and fatigue are common early signs. Pale straw-colored urine is a practical sign that you are well hydrated.
Does food provide water?
It does — fruit, vegetables, soup and yogurt are all meaningful sources, typically covering around a fifth of daily fluid needs.