Water Intake Calculator

The Water Intake Calculator is a web tool that calculates your daily recommended water intake based on five factors: age, gender, weight, activity level, and climate. It follows the standards established by Japan's Ministry of Health, Labor and Welfare (MHLW) "Promote Water Drinking for Health" committee, applying age-specific base rates (18-54 years: 35ml/kg, 55-64 years: 30ml/kg, 65+ years: 25ml/kg).

By combining activity level factors (sedentary to very active), climate adjustments (cool to very hot), and gender-based fine-tuning, the calculator provides highly personalized and accurate hydration recommendations. Results are displayed in three formats: milliliters, liters, and 200ml glass equivalents.

Adequate water intake is essential for maintaining basic body functions such as temperature regulation, nutrient transport, and waste elimination. During hot weather or sports activities, the risk of dehydration and heat stroke increases significantly, making it important to understand scientifically-based hydration needs tailored to your specific situation.

Around the end of Japan's rainy season and during stretches of extreme heat, hydration needs can rise even at the same body weight. Adjust the climate setting before commuting, outdoor work, club activities, or summer travel to estimate a practical daily fluid target.

All processing is performed in your browser with no data transmission to external servers.