Find out how much water to drink a day for your body weight, how active you are and how hot it is where you live. The water intake calculator gives a daily target in litres, glasses and ounces, and adds extra for exercise, summer heat, pregnancy and breastfeeding.
Water intake formula
Worked example
A 70 kg adult needs about 70 × 33 = 2,310 mL as a base. With 30 minutes of exercise (+360 mL) in a hot summer (+500 mL), the target is about 3.2 litres, or 13 glasses, a day.
Reference intakes
| Source | Women | Men |
|---|---|---|
| EFSA (Europe), total water from food and drink | 2.0 L/day | 2.5 L/day |
| US National Academies, total water | 2.7 L/day | 3.7 L/day |
| Pregnancy (EFSA) | +0.3 L/day | — |
| Breastfeeding (EFSA) | +0.7 L/day | — |
People with heart failure or kidney disease may be told to limit fluids, so follow your doctor’s advice first.
For general information only, not medical advice. Talk to a doctor or registered dietitian before major changes to your diet or training, especially if you are pregnant, under 18, or have a health condition.
Frequently asked questions
How much water should I drink a day?
Most adults need about 30–35 mL per kg of body weight, which is roughly 2–3 litres for many people, plus more when it is hot or you exercise.
Do tea, milk and food count towards water intake?
Yes. Tea, milk, juice and water-rich foods like fruit, vegetables, daal and yogurt all count. Food provides about 20% of daily water.
How do I know if I am drinking enough?
Pale yellow urine and rarely feeling thirsty are good signs. Dark urine, headaches and tiredness can mean you need more.
How much extra water do I need when exercising?
Roughly 350–700 mL for every hour of exercise, more in heat. Weigh yourself before and after: each kg lost is about 1 litre of sweat.
Can you drink too much water?
Yes. Drinking many litres in a short time can lower blood sodium (hyponatraemia). Spread intake across the day.
Related tools
Free educational tool by HawkInc. Results are calculated in your browser and rounded for display; check critical work by hand or with a second method.