Water Intake Calculator
Look up the reference amount of water a day for your age and sex, from drinks and from food, in liters, ounces and cups.
The Institute of Medicine's Adequate Intake (AI) for total water, an estimate of typical intake rather than a requirement, is 3.7 liters a day for men and 2.7 liters for women aged 19 and over. About 80 percent of it usually comes from drinks, including plain water: about 3.0 L, or 101 fl oz (about 13 cups), for men and 2.2 L, or 74 fl oz (about 9 cups of 8 fl oz), for women. The rest comes from food.
This calculator shows population reference values for healthy people and is not medical advice or a substitute for a doctor. It does not adjust for your size, activity, climate or any health condition, and people with kidney, heart or other conditions, or who have been told to limit fluids, should follow their doctor's advice.
Adequate Intake of total water
3.7 L a day
- From drinks, including water
- 3.0 L = 101 fl oz, about 13 cups of 8 fl oz
- From food
- 0.7 L
- Total
- 3.7 L = 125 fl oz
A reference value for healthy people, not a personal requirement. Active people and hot weather call for more. Source: Institute of Medicine, Table S-2.
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About the Water Intake Calculator
There is no single amount of water everyone must drink. The figures here are Adequate Intakes from the Institute of Medicine's 2005 Dietary Reference Intakes for water: the median total water intake of healthy people in a national survey. Total water counts plain water, other drinks and the water in food, so the calculator splits it into the part from drinks and the part from food. For adults 19 and over the reference is 3.7 L a day for men and 2.7 L for women; pregnancy raises it to 3.0 L and breastfeeding to 3.8 L. The reference for ages 4 to 8 is lower, at 1.7 L a day. The report says the AI is not a specific requirement and that intake below it may not add risk for healthy people, while people who are physically active or out in the heat need more.
Frequently asked questions
Do coffee and tea count toward water intake?+
Yes. The reference counts water from all drinks and from food. The report says the diuretic effect of caffeinated and alcoholic drinks may be transient in nature, and that these drinks still contribute to total water.
Is it 8 glasses a day?+
Not as a rule. For adult women the reference from drinks is about 9 cups of 8 fl oz and for adult men about 13. The reference is not a requirement, and heavy activity and hot weather raise the need, so the figures are a guide only.
Why is the amount from food included?+
Fruit, vegetables, soup and other foods contain water, and in the survey behind these figures food supplied roughly a fifth of total water. If you eat less of those foods, more of your water comes from drinks.
Can you drink too much water?+
The report sets no upper limit. It notes that a person with normal kidney function can excrete at most about 0.7 L of water an hour. Ask a doctor about any limit that applies to you.
Adequate Intakes for total water, from beverages and from food, by life stage and sex, and the statement that the AI is not a specific requirement: Institute of Medicine, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005), Summary and Table S-2. National Academies Press, doi:10.17226/10925.
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