Free tool
Water Intake Calculator: How Much Water Do You Need?
See the National Academies daily total water target for your age and life stage, in liters and cups, and how much typically comes from beverages versus food.
This page is for general education and is not medical advice. Talk with your clinician or a registered dietitian before major diet changes or starting supplements, especially if you take medication, are pregnant, or have a chronic condition. See our medical disclaimer.
Find your daily water target
Choose a group to see your total daily water target.
Total water by age and life stage
| Group | Total water (L a day) | Cups (8 fl oz) |
|---|---|---|
| Children 1 to 3 | 1.3 | 5.5 |
| Children 4 to 8 | 1.7 | 7.2 |
| Boys 9 to 13 | 2.4 | 10.1 |
| Girls 9 to 13 | 2.1 | 8.9 |
| Boys 14 to 18 | 3.3 | 13.9 |
| Girls 14 to 18 | 2.3 | 9.7 |
| Men 19 and older | 3.7 | 15.6 |
| Women 19 and older | 2.7 | 11.4 |
| Pregnancy (14 to 50) | 3.0 | 12.7 |
| Breastfeeding (14 to 50) | 3.8 | 16.1 |
What counts toward your water
- Beverages: water, milk, unsweetened tea and coffee, and other drinks. Choose water most often and limit sugary drinks.
- Food: fruits and vegetables such as watermelon, oranges, cucumbers and lettuce are mostly water, and soups and yogurt add more.
- You may need more: in hot or humid weather, at higher altitude, during long exercise, and with fever, vomiting or diarrhea.
⚠️ Fluid limits and warning signs
Some conditions, including heart failure and kidney disease, can require limiting fluids. Follow your clinician’s advice. Seek medical care for signs of dehydration such as confusion, fainting, very dark urine or not passing urine.
Common questions
How much water should I drink a day?
The National Academies set an Adequate Intake of about 3.7 L of total water a day for men and 2.7 L for women aged 19 and older. This counts water from all beverages and food. On average about 20% comes from food, so roughly 3.0 L (about 13 cups) of beverages for men and 2.2 L (about 9 cups) for women.
Is the 8 glasses a day rule correct?
Eight 8-ounce glasses (about 1.9 L) is a handy rule of thumb, but it is not an official requirement. Total needs depend on your size, activity, climate, diet and health, and the water in food and other drinks counts.
Does coffee or tea count?
Yes. The National Academies note that caffeinated beverages contribute to total water intake for most people. Water, milk, unsweetened tea and coffee, and the water in fruits and vegetables all count. Limit sugary drinks.
How do I know if I am drinking enough?
For most healthy people, drinking to thirst and having pale-yellow urine are practical signs. You may need more in hot weather, at altitude, during illness with fever, vomiting or diarrhea, or when exercising for long periods.
Who should follow different fluid advice?
People with heart failure, kidney disease, certain hormonal conditions, or who take diuretics are sometimes told to limit or adjust fluids. Follow your care team’s advice. Contact a clinician for signs of dehydration, such as confusion, dizziness, very dark urine or no urine.
Cite or link to this tool
HealAtlas Team. Water Intake Calculator. HealAtlas. https://healatlas.com/nutrition-calculators/water-intake-calculator/
Related on HealAtlas
Sources
- National Academies: Dietary Reference Intakes (DRIs): RDAs and AIs for total water and macronutrients
- National Academies Press: Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005)
- Dietary Guidelines for Americans, 2020-2025 (USDA/HHS)
- NIH MedlinePlus: Water in diet
- Harvard T.H. Chan School of Public Health, The Nutrition Source: How Much Water Do You Need?