Water Intake Calculator
Calculate daily hydration requirements based on body mass, exercise, and climate
Equivalent to 100 fluid ounces per day
Mathematical Formula & Scientific Methodology
Formula: Biometric Fluid Replacement Standard (EFSA / NASEM)
Total Water = (Weight kg × 35 ml) + [(Exercise min / 45) × 500 ml] × Climate FactorAccounts for both obligatory urinary/respiratory losses and active thermoregulatory sweating.
Model Assumptions
- Includes all water from plain water, beverages, and moisture in food (~20% of total)
Variables & Standard Units
| Symbol | Physiological Meaning | Unit |
|---|---|---|
| 35 ml/kg | Baseline metabolic water turnover | ml/kg |
| 500 ml | Average fluid lost per 45 minutes of moderate physical activity | dimensionless |
Scientific Limitations
- High sweat rates in endurance athletes can reach 1.5–2.5 L/hr, requiring personalized sweat-rate testing
Peer-Reviewed Scientific Citations
A new predictive equation for resting energy expenditure in healthy individuals (1990)
Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO (1990) — The American Journal of Clinical Nutrition, 51(2), 241-247
Key Finding: Mifflin-St Jeor equation is accurate within ±10% of measured REE in non-obese and obese individuals, recommended by the Academy of Nutrition and Dietetics as the most reliable standard equation.
Frequently Asked Questions
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