About the Water Intake Calculator
Staying properly hydrated supports nearly everything your body does — regulating temperature, cushioning joints, transporting nutrients, and keeping concentration and energy levels steady. But "drink eight glasses a day" is a one-size-fits-all rule that ignores the fact that a 50 kg person and a 100 kg person don't need the same amount of water.
This calculator uses a simple, weight-based baseline — about 35 mL of fluid per kilogram of body weight per day — a practical guideline commonly used for estimating healthy adult fluid needs, then adds an activity-level adjustment on top, since exercise increases fluid loss through sweat. Unlike calorie-burn formulas, there's no single universally standardized number for exactly how much extra fluid each activity level requires, so this adjustment is a practical estimate rather than a precise physiological calculation.
The result shown is fluid/beverage intake specifically — it doesn't include the roughly 20% of daily water most people get from food. Treat this as a helpful daily target rather than a strict requirement: individual needs shift with climate, health conditions, and how your body responds, so adjust based on thirst, urine color, and how you feel rather than chasing the exact number.
Baseline of 35 mL per kg of body weight per day is a widely used practical hydration guideline for healthy adults, broadly consistent with the U.S. National Academies of Medicine's 2004 Dietary Reference Intakes for total water. Activity-level adjustment reflects general fluid-replacement guidance (e.g. American College of Sports Medicine) rather than a single standardized figure.