Hydration Calculator
Estimate daily water needs from weight, activity, and climate.
Input Data
Results
At a glance:Base = weight × 35 ml/kg; extra = exercise (12 ml/min) + hot climate (500 ml); total = base + extra − foodWater (≈20% of base). Cups = total ÷ 250.
Formula
base = weight × 35.
extra = activityMinutes × 12 + (climate==hot ? 500 : 0).
total = base + extra − base × 0.2.
cups = total ÷ 250.
How to Use
- Enter weight, exercise minutes, and climate.
- The tool estimates total water and cups.
Case Studies
70 kg, 30 min exercise, normal climate
base = 70 × 35 = 2450 ml.
extra = 30 × 12 = 360 ml.
total = 2450 + 360 − 490 = 2320 ml.
cups ≈ 9.3.
FAQ
Why 35 ml/kg?
A common rule of thumb; active or hot-climate people need more. Adjust to thirst and urine colour.
What counts as food water?
About 20% of daily needs come from food; the tool credits that automatically. You can also enter a custom value.
Is more always better?
No. Excess water can cause hyponatraemia. Stay within a reasonable range and follow thirst.
Who needs more?
Endurance athletes, people in hot climates, and those who are pregnant or breastfeeding may need more.
Is this medical advice?
No. It is a general estimate. Consult a professional for specific conditions.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.