Daily Water Intake Calculator
Hydration needs depend on a mix of body size, activity, and ambient temperature. This calculator estimates total liters per day by combining a base recommendation of 35 ml per kilogram of body mass, 12 ml per minute of moderate-to-vigorous exercise, and an extra 100 ml per degree Celsius when temperatures rise above 25°C. These factors capture the increased sweat rate and respiratory water loss that come with larger bodies, longer workouts, and hotter climates.
How the Formula Works
- Base hydration: weight × 0.035 converts to liters using widely cited 35 ml per kg guidelines.
- Exercise adjustment: activity minutes × 0.012 adds ~12 ml per minute to make up for sweat losses.
- Heat bonus: for every degree above 25°C, the body needs an extra 0.1 liters to stay cool and maintain blood volume.
Example
If you weigh 70 kg, train for 45 minutes, and the temperature averages 30°C, the calculator estimates 70×0.035 = 2.45 L base water, plus 45×0.012 = 0.54 L for exercise, plus (30-25)×0.1 = 0.5 L for heat. Total suggested intake: 3.49 liters per day.