How it is calculated
- Base: about 30 ml per kg of body weight (at least 1.5 L).
- Training: +0.5 L per hour of moderate exercise, +0.75 L per hour of hard exercise.
- Heat: +0.5 L on warm days, +1 L in hot weather or with sauna.
For comparison, the European Food Safety Authority sets about 2.0 L of total water a day for women and 2.5 L for men, from drinks and food together. Needs differ from person to person, so use the number as a starting point.
During training
Drink a glass of water 1–2 hours before exercise. During long or hot sessions, sip small amounts every 15–20 minutes instead of drinking a lot at once. After training, drink to thirst; if you sweat a lot, a salty snack or a drink with electrolytes helps.
Signs to watch
Thirst, dark urine, headache and tiredness can mean you drink too little. Swollen hands, nausea and confusion after drinking large amounts can mean too much. Spread drinking over the day.
Questions and answers
Do tea and coffee count?
Yes. Tea, coffee, milk and other drinks count toward your daily water. Moderate amounts of coffee do not dehydrate you.
Is 2 litres a day right for everyone?
No. A heavier or more active person needs more, a lighter person less. The calculator adjusts the goal to your weight, training and weather.
Can I drink too much water?
Yes. Drinking several litres in a short time can lower blood sodium, which is dangerous. Do not drink more than about 1 L per hour.
How it is calculated: sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for water. EFSA Journal. 2010;8(3):1459.
- American College of Sports Medicine; Sawka MN et al. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377–390.
- National Academies. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. 2005.
Gymvert gives general information for healthy adults. It is not medical advice. If you have a health condition, are pregnant, or are unsure, talk to a doctor before changing your training or diet.