Water Intake Calculator
Calculate your recommended daily water intake based on weight and exercise.
Assumptions used in this calculation
- General guideline: Individual needs vary with climate, health conditions, and diet, this is a general starting point, not medical advice.
About this calculator
"Drink eight glasses a day" is the advice everyone's heard, but it ignores that hydration needs actually scale with body size and activity, a larger or more active person simply needs more fluid than the one-size-fits-all number suggests. This calculator instead uses the common clinical guideline of roughly 35ml of water per kilogram of body weight as a base, then adds 350ml for every 30 minutes of exercise to account for fluid lost through sweat. Enter your body weight and typical daily exercise time, and it returns a personalized daily water target in litres. It's a far quicker way to get a body-weight-adjusted number than looking up the guideline and doing the multiplication yourself, and it avoids both the generic "eight glasses" rule and the risk of underestimating needs on heavy training days. Individual needs still vary with climate, health conditions and diet, so treat the result as a practical starting point rather than a strict prescription.
Worked example
70 kg, 30 minutes of exercise/day
Result: Recommended intake ≈ 2.8 L/day
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