Water Intake Calculator
Calculate how much water you should drink each day free. Enter your weight and activity level to get your daily target in litres and glasses. No signup, everything runs in your browser.
Your result will appear here
Your daily water target
Base intake is 35 ml per kilogram of body weight, plus extra for activity. Hot weather, illness and pregnancy increase your needs — listen to your body and your doctor.
How to use
- Enter your weight in kilograms.
- Choose your activity level, then click Calculate Water Intake.
- See your daily target in litres, millilitres and standard 250 ml glasses.
Frequently asked questions
How is my water intake calculated?
The base is 35 ml of water per kilogram of body weight per day, which is a commonly used guideline. Extra water is added for activity — from 0 ml for a sedentary day up to 1,000 ml for very hard training.
Does food count toward my water intake?
Yes. Around 20% of the water most people take in comes from food, especially fruit, vegetables and soups. This calculator gives a drinking-water target, so food is a bonus on top.
Can I drink too much water?
Yes, though it is rare. Drinking far more than you need in a short time can dilute the sodium in your blood (hyponatraemia). Spread your intake through the day and do not force large amounts at once.
Do tea and coffee count?
Mostly yes — caffeinated drinks still hydrate you, despite the old myth. Plain water is still the best choice, but tea and coffee do contribute to your daily fluid intake.