Water Intake Calculator: How Much Water Should I Drink?
This water intake calculator estimates how much water you should drink each day from your body weight, how much you exercise and how hot it is where you live. See the answer in liters, ounces, cups and glasses, and spread it across your waking hours.
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Quick answer: A common guide is about 30 to 35 ml of water per kilogram of body weight (roughly half an ounce per pound), plus about 350 ml (12 oz) for every 30 minutes of exercise. For a 70 kg (154 lb) adult that is around 2.3 liters, or about 10 cups, before exercise.
How to use the water intake calculator
- Enter your weight in kilograms or pounds.
- Add how many minutes you exercise on a typical day.
- Choose your climate. Heat, humidity, altitude and dry air all raise your needs.
- Read your daily total in liters, ounces, cups and glasses, and how much to sip each waking hour.
How much water do adults need?
The US National Academies suggest a total daily fluid intake of about 3.7 liters for men and 2.7 liters for women, counting water from all drinks and food. About 20 percent normally comes from food such as fruit, vegetables and soup, which leaves roughly 3 liters (13 cups) of drinks for men and 2.2 liters (9 cups) for women. The old “8 glasses a day” rule is a reasonable, easy-to-remember minimum.
When you need more water
- Exercise: drink before, during and after. Long or intense sessions may also need electrolytes.
- Hot weather or saunas: sweating can lose a liter or more an hour.
- Pregnancy and breastfeeding: about 300 ml and 700 ml extra a day.
- Illness: fever, vomiting and diarrhea all increase fluid loss.
Signs of dehydration
Thirst, dark yellow urine, headache, tiredness and dizziness are early signs. Pale straw-colored urine usually means you are drinking enough. Drinking far more than you need in a short time can also be harmful, so spread water across the day rather than drinking large amounts at once.
If you have kidney, heart or liver disease, or take medicine that affects fluid balance, follow your doctor’s advice on how much to drink; this calculator is general information only. Related health tools: the calorie calculator, BMI calculator and sleep calculator.
FAQ
Do tea and coffee count?
Yes. Moderate amounts of tea and coffee count toward your fluid intake, although water is the best everyday choice.
How many ounces of water should I drink?
Half your body weight in pounds, in ounces, is a quick rule. A 160 lb person would aim for about 80 oz a day.