How the Formula Works

The baseline calculation multiplies your body weight in kilograms by 30-35 milliliters. This produces a range that accounts for individual variation in metabolism, body composition, and baseline hydration needs.

We then apply an activity multiplier. Physical exercise increases water loss through sweat. A sedentary person's needs are at the baseline, while a very active athlete may need up to 80% more water.

Climate plays a significant role too. Hot and humid conditions can increase sweat production dramatically, while cold, dry air accelerates respiratory water loss.

This calculator provides a science-based estimate. Your actual needs may differ based on diet, medications, health conditions, and pregnancy or breastfeeding status.