How much water do I need each day?
It depends on the person. The CDC says daily water needs vary with age, sex, pregnancy, activity and breastfeeding. For young adults aged 19 to 30, the Institute of Medicine sets an Adequate Intake of total water of 3.7 liters (men) and 2.7 liters (women), which includes water from food.
Action level No action usually needed
- Why you are seeing it
- It is a common question, often answered with a round number such as eight glasses.
- Why it matters
- A published reference separates the water in food from the water in drinks, so the figure for drinks alone is lower than the total.
- What should I do?
- See the reference figures in the Water Intake Information tool.
- Remember the reference covers ages 19 to 30 only here, and needs differ with age and activity.
- Ask a doctor about your own needs, especially with a medical condition or a medicine.
- A common misunderstanding
- The total water figure includes the water in food, so it is not the same as the amount to drink.
Why one number cannot be right
The CDC says daily water intake recommendations vary by age, sex, pregnancy status, activity level and breastfeeding status. A single figure for everyone would be wrong for most people.
A simple example
Liters to cups
2.7 liters x 33.814 = about 91 US fluid ounces, or 11.4 cups of 8 fl oz.
81% of 2.7 liters is about 2.2 liters from drinks, or 74 fluid ounces.
The remaining 0.5 liters came from food in the survey data.
The published reference for young adults
The Institute of Medicine (2005) sets an Adequate Intake for total water for young men and women aged 19 to 30 of 3.7 and 2.7 liters a day. Total water means water from drinks and from food together.
The values come from survey data on what people in the United States actually take in. About 81% came from beverages and about 19% from food.
Try these tools
- Water Intake InformationSee the general reference for total daily water from drinks and food, in liters, cups and ounces.