About this tool
A common rule of thumb is 30 to 35 ml of water per kilogram of body weight each day. This calculator multiplies your weight by 30 and 35 to give a range, then adds about 350 ml for every 30 minutes of exercise and 250 or 500 ml for warm or hot, humid weather. For example, a 60 kg person who exercises for 30 minutes on a hot day needs about 1,800 to 2,100 ml as a base, plus 350 ml for exercise and 500 ml for the heat, so roughly 2.7 to 3.0 litres, or about 13 to 15 cups of 200 ml. The amount includes water from food, soup, tea and coffee, so you do not need to drink all of it as plain water. Needs vary with age, pregnancy, breastfeeding and health. People with kidney, heart or liver disease, or on a fluid limit, should follow their doctor's advice. This is a general guide and not medical advice. Children should follow their pediatrician's advice. Your data is never sent anywhere.
How to use
- Enter your body weight in kilograms.
- Enter today's exercise minutes and choose the weather.
- Read the daily range in litres, millilitres and 200 ml cups.
- Spread your drinking through the day instead of all at once.