How it's calculated
The calculator looks up the Adequate Intake (AI) of total water that the National Academies' Food and Nutrition Board set for your age and sex, and for pregnancy and breastfeeding.National Academies It then converts liters to US cups and fluid ounces.
Total water means all water you take in: the water in food, in beverages and in plain drinking water. It is not the amount you need to drink on top of everything else.
This is general nutrition information, not medical advice.
The formula
There is no formula: the values come straight from the National Academies table.
| Life stage | Total water (liters a day) |
|---|---|
| Children 1–3 years | 1.3 |
| Children 4–8 years | 1.7 |
| Males 9–13 | 2.4 |
| Males 14–18 | 3.3 |
| Males 19 and older | 3.7 |
| Females 9–13 | 2.1 |
| Females 14–18 | 2.3 |
| Females 19 and older | 2.7 |
| Pregnancy | 3.0 |
| Breastfeeding | 3.8 |
Cups = liters × 1,000 ÷ 236.5882 mL per US cup. Fluid ounces = liters × 1,000 ÷ 29.57353 mL per US fluid ounce, using NIST conversion factors.NIST
Worked example
A woman aged 30 has an AI of 2.7 L of total water a day, about 11.4 cups. During pregnancy that rises to 3 L, and while breastfeeding to 3.8 L.
Adequate Intake of total water: 3.7 LITERS A DAY · ABOUT 15.6 CUPS
Assumptions and limitations
- An Adequate Intake, not an exact requirement. The National Academies describe an AI as believed to cover the needs of all individuals in the group, while noting the data are too limited to say with confidence what share of people it covers.
- Food counts. Because the AI is total water, the water in fruit, vegetables, soups and other foods counts toward it.
- Healthy people. The values are for healthy people. If you have heart, kidney or other conditions, or a doctor has told you to limit fluids, follow their advice.
- Ages 1 and up. The National Academies also list values for infants, but this calculator starts at age 1.
The calorie calculator and macro calculator cover the rest of the daily picture.