Most women need about 2.2 litres and most men about 3 litres of fluid a day from drinks. You need more when you exercise, in hot weather, and when pregnant or breastfeeding.
How this calculator works
The starting point is the US National Academies Adequate Intake for total water: 3.7 litres a day for men and 2.7 litres for women. About 20% of that usually comes from food, so the calculator shows the rest as drinks. All drinks count, including tea, coffee and milk.
It then adds about 0.5 litres for each hour of exercise and 0.5 litres for hot conditions. Sweat losses vary a lot from person to person, so treat these as rough guides. Pale yellow urine is a simple sign you’re drinking enough.
Who should be careful
- People with heart failure or kidney disease may be told to limit fluids. Follow your doctor’s advice.
- Drinking very large amounts quickly, especially during long endurance events, can cause dangerously low blood sodium.
Sources
- Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press, 2005.
- American College of Sports Medicine; Sawka MN, et al. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390.