Data & Methodology

HydrationMap calculates daily water intake using the following peer-reviewed formula structure (Galvez-based model with weather and physiology adjustments):

Daily Intake (ml) =
(Weight × Age Fluid Factor)
+ Sex + Pregnancy + Breastfeeding + Menstruation
+ Activity + Temperature + Humidity + Altitude
+ Medication + Illness + Alcohol + Caffeine
bounded by age and weight safety limits

Variables include body weight, age, sex, activity level, temperature, relative humidity, altitude, illness status, medication profile, caffeine intake, and alcohol intake.

• Primary weather source: WeatherAPI (`temp_c`, `humidity`, `uv`, plus condition and wind context).
• Refresh cadence: weather values are refreshed hourly for city-level recommendations.
• City coverage: 480 cities across 100+ countries (currently 103 countries in our dataset).
• Accuracy statement: outputs are evidence-informed estimates for healthy users, not a medical diagnosis.

HydrationMap uses a modified version of the Galvez Equation as its baseline, adjusted dynamically for environmental factors. The standard "8x8 rule" (8 glasses of 8 ounces) is insufficient for active individuals or those living in extreme climates.

Key Variables

• Base Metabolic Needs: Calculated using body weight and activity level.
• Temperature Adjustment: For every 1°C above 20°C, fluid requirements increase by approximately 100-150ml.
• Humidity Factor: Low humidity (<30%) increases insensible water loss through respiration and skin evaporation.
• Altitude Factor: At elevations above 1,500m, respiration rates increase, leading to 200-400ml additional daily fluid loss.
• Solar Radiation: UV index data is used to estimate direct sun exposure effects on body temperature regulation.

The information provided by HydrationMap is for educational and informational purposes only and is not intended as medical advice. Individual hydration needs can vary significantly based on medical conditions (such as kidney disease or heart failure), medications, and pregnancy.

Always consult with a healthcare professional before making significant changes to your diet or fluid intake, especially if you have pre-existing health conditions.