How much water should I drink a day?
Short answer
The National Academies set an adequate intake of about 3.7 liters of total water a day for men and 2.7 liters for women. That counts water from all drinks and food, not just plain water. About 80 percent usually comes from drinks, or roughly 3 liters for men and 2.2 for women. For most healthy people, thirst and drinking with meals are enough.
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How much water do adults need?
About 3.7 liters of total water a day for men and 2.7 liters for women, according to the National Academies' Dietary Reference Intakes. These are Adequate Intakes, set from national data showing that adequately hydrated adults took in about these amounts on average. An Adequate Intake is believed to cover the needs of all healthy people in a group, but gaps in the data mean it isn't a precise requirement.
| Group | Total water a day |
|---|---|
| Men, 19 and older | 3.7 L (about 125 oz) |
| Women, 19 and older | 2.7 L (about 91 oz) |
| Pregnancy | 3.0 L (about 101 oz) |
| Breastfeeding | 3.8 L (about 128 oz) |
The panel that set these values chose not to give a rule of thumb for glasses of water. Its chair explained that hydration needs can be met from many sources besides drinking water, and that most people get enough through normal drinking habits and by letting thirst guide them.
Does the water in food count?
Yes. The National Academies' figures are for total water, which includes the moisture in food, and about 20 percent of the average person's water comes from food. USDA FoodData Central lists raw broccoli at 89 percent water and cooked white rice at 68 percent. The 2020–2025 Dietary Guidelines likewise note that water in fruits, vegetables and soups counts toward fluid intake.
Do coffee and tea count?
Yes. The National Academies panel concluded that caffeinated drinks count toward hydration as much as caffeine-free ones. It found that caffeine's effect on urine output may be temporary and that there's no convincing evidence it causes a build-up of water loss.
Caffeine has its own limit. The 2020–2025 Dietary Guidelines note that the FDA has cited 400 milligrams a day as an amount not generally linked to dangerous effects in healthy adults.
When do you need more?
When you're very active, in the heat, pregnant or breastfeeding. The National Academies note that very physically active people and people in hot climates may need more, and that very active people continually exposed to hot weather often need 6 liters or more of total water a day. Needs also rise to 3.0 liters in pregnancy and 3.8 liters while breastfeeding.
Older adults need to pay closer attention. The 2020–2025 Dietary Guidelines point out that the sense of thirst tends to decline with age, and that adults 60 and older drink about 2 fewer cups of fluid a day than younger adults, mostly because they drink less water.
Can you drink too much?
It's possible but unusual. The National Academies panel noted that some athletes in strenuous events and some people with certain psychiatric conditions occasionally drink enough water to be life-threatening. If you have a heart or kidney condition, ask your clinician how much fluid is right for you.
What should you drink?
Mostly water and unsweetened drinks. The 2025–2030 Dietary Guidelines advise choosing water, still or sparkling, and unsweetened beverages, and avoiding sugar-sweetened ones. Drinks can carry a lot of calories: the 2020–2025 guidelines list 156 calories in a 12-ounce regular soda and 238 in a 12-ounce fruit drink, compared with none in plain water or unsweetened tea.
Common questions
Do I need to drink eight glasses of water a day?
No. The National Academies panel deliberately gave no glasses-per-day rule, because water from food and other drinks counts too, and thirst keeps most healthy people hydrated.
Does sparkling water count?
Yes. The 2025–2030 Dietary Guidelines name water "still or sparkling" as the first choice for hydration.
How can I tell if I'm drinking enough?
For most healthy people, drinking when thirsty and having something with meals is enough, according to the National Academies. Older adults, whose thirst may be weaker, and people who sweat heavily should drink more deliberately.
Sources
- National Academies of Sciences, Engineering, and Medicine (Institute of Medicine). Report sets dietary intake levels for water, salt, and potassium to maintain health and reduce chronic disease risk. News release, February 11, 2004. nationalacademies.org
- National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Sodium and Potassium, Appendix J: Dietary Reference Intakes Summary Tables. 2019. nationalacademies.org
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2025–2030. cdn.realfood.gov
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025. web.archive.org
- U.S. Department of Agriculture, FoodData Central. Broccoli, raw (FDC ID 170379). fdc.nal.usda.gov
- U.S. Department of Agriculture, FoodData Central. Rice, white, long-grain, regular, unenriched, cooked without salt (FDC ID 169757). fdc.nal.usda.gov
Estimates, not medical advice. If you're pregnant, have a medical condition or have a history of disordered eating, talk to a clinician before changing how you eat.
Written by the SeeMeEat editorial team under a pen name.