Water Intake Calculator
Compute daily water needs from weight, activity, and climate. Drink the right amount, not 8 glasses blindly — free, local, no signup.
How to Use the Water Intake Calculator
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Frequently Asked Questions
How much water daily?
Base 35 mL per kg (70 kg needs ~2.5L) times a climate factor of 0.9–1.3, plus 12 mL per exercise minute. Defaults (70 kg, 30 min, moderate) total 2,810 mL (2.8L, ~12 cups). Thirst plus pale-yellow urine calibrates personally.
Is 8 glasses right?
Coincidentally close for average adults, wrong for most individuals. Weight-based math beats one-size rules.
Exercise adjustment?
About 720 mL per hour of activity (12 mL per minute), multiplied further in heat. Weigh before/after long sessions to dial personal rates.
Do hydration targets upload?
No — math runs locally in your browser. Health data never leaves your device.
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Last updated October 2026