Daily Hydration
Water Intake Calculator
How much water you actually need based on bodyweight and how much you sweat. Goodbye to the lazy '8 glasses a day' rule.
Daily target
103fl oz
Liters
3.04
Fluid oz
103
8oz cups
13
The Hydration formula
Baseline: 35 ml × bodyweight (kg) National Academy of Medicine guideline.
Activity bonus: +250 ml (light) up to +1000 ml (athlete) to replace sweat losses.
Hot/humid weather adds 500–1000 ml more. Altitude above 8,000 ft adds 500 ml. Pregnancy and breastfeeding both increase needs significantly.