Water Intake Calculator
Recommended intake
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Water Intake Calculator: Liters per Day from Weight
Estimate daily fluid from weight, activity, and heat. Enter Weight (kg or lbs), Activity level, and toggle Hot weather when it applies. The page shows Recommended intake in liters per day plus an approximate cup count. Planning aid only. Thirst, urine color, and medical conditions matter more than any single formula.
How to use
The tool starts near 33 ml per kg body weight, then adds a fixed liter bump for activity: Light +0.3 L, Moderate +0.5 L, Active +0.8 L, Very Active +1.2 L, Sedentary adds none. Hot weather adds another 0.5 L. Cups are derived from liters for quick reference, not a separate measurement system.
Example
75 kg, Moderate activity, hot weather off gives about 3.0 L per day (roughly 13 cups on the page). The same person on Very Active with hot weather on rises toward about 4.2 L.
Tips
Spread intake through the day. Coffee and tea still count toward fluids for most people. Pregnancy, breastfeeding, fever, and kidney or heart conditions need clinician advice, not this estimate alone.