How the water calculator works
- Your weight: 33 ml for each kilogram (about 0.5 fl oz per pound).
- Exercise: 350 ml (12 fl oz) for every 30 minutes.
- Heat: 500 ml more on hot or humid days. Pregnancy adds about 300 ml, breastfeeding about 700 ml.
Example
A person who weighs 70 kg and exercises for 30 minutes needs about 70 × 33 = 2,310 ml, plus 350 ml: 2.7 litres a day, or about 11 glasses.