Get a simple daily water intake starting point based on your body weight and exercise, in ounces, liters and glasses.
How much water should you drink?
There is no single number that fits everyone. Needs depend on body size, activity, climate, diet and health. The U.S. National Academies estimated adequate total water intake (from all drinks and food) at about 3.7 liters a day for men and 2.7 liters for women. This calculator gives a personal starting point for drinking water based on your weight and exercise.
Starting point (liters) ≈ body weight (kg) × 0.033 + 0.35 L per 30 minutes of exercise
Worked example
A person weighing 154 lb (69.9 kg) gets a baseline of about 2.3 liters. Adding 30 minutes of exercise brings it to about 2.66 liters, roughly 90 fl oz or 11 cups across the day.
Signs you are well hydrated
- You rarely feel thirsty.
- Your urine is pale yellow.
- You are not getting headaches or feeling unusually tired.
When you may need more
- Hot or humid weather, or high altitude
- Long or intense exercise (consider electrolytes for sessions over about an hour)
- Illness with fever, vomiting or diarrhea
- Pregnancy and breastfeeding (ask your healthcare provider)
Some people, such as those with heart or kidney conditions, may need to limit fluids. Follow your doctor's advice.
Frequently asked questions
Do coffee and tea count?
Yes. Despite their mild diuretic effect, they still contribute to your daily fluid intake. So do milk, soups and water-rich foods.
Can you drink too much water?
Yes, though it is rare. Drinking very large amounts in a short time can lower blood sodium. Spread your intake through the day.
Related tools
These calculators give estimates for healthy adults based on published formulas. They are not medical advice. Talk to a doctor before making major changes to your diet or exercise, especially if you are pregnant, under 18 or have a health condition.