Water Intake Calculator
Estimate how much water to drink each day from your weight and activity.
- Glasses (250 ml)
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- Millilitres
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How much water should you drink?
A common rule of thumb links daily water needs to body weight and activity.
This calculator uses roughly 33 ml per kg of body weight and adds about
350 ml for every 30 minutes of exercise to account for fluid lost through sweat.
Litres and glasses
The result is shown in litres, millilitres and standard 250 ml glasses so it is easy to track through the day. Hot weather, illness and pregnancy can all raise your needs above this baseline.
Note: This is a general estimate, not medical advice. Your ideal intake depends on your health, climate and medications — check with a qualified professional if you are unsure.
How to use the Water Intake Calculator
- Enter your weight. Type your body weight in kilograms.
- Add your activity. Enter your typical daily exercise in minutes.
- Read your target. See your suggested daily water in litres and glasses.
- Adjust for conditions. Drink more in heat, during illness, or with intense training.
Frequently asked questions
Do other drinks count towards this?
Water from tea, coffee, milk and food all contributes to hydration. This figure is a total fluid guide, not water alone.
Can I drink too much water?
Very large amounts in a short time can dilute blood sodium, which is dangerous. Spread intake through the day and follow professional advice if you have kidney or heart conditions.
Why does activity increase the target?
Exercise raises fluid loss through sweat and breathing, so the calculator adds around 350 ml for each 30 minutes of activity.
Is my data stored?
No. The calculation happens entirely in your browser and nothing is sent to a server.