Daily Water Intake Calculator
From body weight, activity level and climate: recommended daily water intake in liters and 250 ml glasses.
Result
How it is calculated
The estimate starts with 30 ml × body weight in kg and adds fixed extras: activity low adds 0 ml, medium adds 500 ml and high adds 1000 ml; climate normal adds 0 ml and hot adds 500 ml. The total in millilitres is divided by 1000 for litres and by 250, rounded to a whole number, for glasses. Weight must be in kilograms and above zero; an unrecognised activity or climate value counts as no extra. The figure is a general guide for a healthy adult, not medical advice. Illness, pregnancy, breastfeeding, medication or kidney and heart conditions can change real needs, so follow a doctor's advice in those cases.
Worked example
A person weighs 70 kg, has medium activity and lives in a hot climate. Base: 30 × 70 = 2100 ml. Activity adds 500 and climate adds 500, giving 3100 ml. In litres that is 3.10 L. In glasses of 250 ml, 3100 / 250 = 12.4, rounded to 12 glasses.
Common mistakes
- Entering weight in pounds; the tool expects kilograms, so the amount comes out about 2.2 times too high.
- Counting every drink the same: whether coffee, tea or food moisture count toward the total is your decision.
- Adding hot-weather or exercise extras twice, once in the tool and once by hand.
- Treating the glasses figure as exact; it is the total rounded to 250 ml glasses.
- Using the result as medical advice for illness, pregnancy or any condition where a doctor has set a limit.
About this calculator
This calculator estimates how much water your body needs each day based on your body weight, how active you are, and the climate you live in — since larger bodies, harder workouts, and hotter or more humid weather all increase fluid loss through sweat and breathing. It converts that estimate into both liters and standard 250 ml glasses so the number is easy to track through the day.
It is useful for athletes and gym-goers planning hydration around training, people living in hot climates or through heatwaves, and anyone simply trying to build a consistent water habit instead of guessing at the old "eight glasses a day" rule, which does not account for individual body size or conditions.
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