How Much Water Should I Drink a Day?
Calculate the daily amount of water by weight and activity.
Tip: Simple rule: ~35 ml of water for every kg of body weight, plus extra when you exercise or it is hot.
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About this digital tool
The daily water calculator tells you how many litres of water to drink each day according to your weight and the amount of exercise. The basic rule is about 35 ml for each kilogram of body weight, so a 70 kg person needs about 2.45 litres, with roughly 350 ml added for every 30 minutes of physical activity.
The result is given in litres and in 250 ml glasses, which is easier to follow through the day. It is a general guide for healthy adults: needs rise with heat, altitude, fever or breastfeeding, while some conditions (heart, kidney) require fluid restriction. In such cases follow your doctor's advice.
How to use
- Enter your body weight.
- Add your minutes of exercise per day.
- See the recommended amount of water in litres.
Frequently asked questions
Do other drinks count too?
Tea, juices and water-rich foods contribute to hydration, but plain water remains the best source with no calories or sugar.
How many litres of water should I drink a day?
For healthy adults the estimate is about 35 ml per kg of weight, so usually 2-3 litres a day, plus extra water when you exercise. Part of this also comes from food and other drinks.
Should I drink more water when I exercise?
Yes. This calculator adds about 350 ml for every 30 minutes of exercise. In hot weather or long workouts even more may be needed.
Can I drink too much water?
Yes, in rare cases drinking too much water in a short time can upset the salt balance. Drink gradually through the day and follow your thirst. If you have heart or kidney disease, ask your doctor.