Daily water needs vary based on body weight and activity level, and while there's no single universally exact number that fits everyone, a common baseline is roughly 30–35 milliliters of water per kilogram of body weight, adjusted upward for higher activity levels that increase fluid loss through sweat.
This calculator applies that baseline formula and a simple activity multiplier to give a reasonable daily water target in both liters and standard 240ml cup equivalents.
Keep in mind this is a general guideline rather than medical advice — factors like climate, individual health conditions, and diet (since food also contributes water) all affect real hydration needs, so adjust based on thirst and how you feel.
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Frequently asked questions
Does this include water from food?
No, this estimates water intake from drinking specifically; food, especially fruits and vegetables, also contributes meaningfully to overall hydration.
Should I drink exactly this amount every day?
Treat it as a general guideline — actual needs shift with weather, health conditions, and how active you are on a given day, so listening to thirst remains important too.