The reference intake for an adult man is 3.7 L of total water a day, about 3.0 L of it from drinks. For an adult woman it is 2.7 L, about 2.2 L from drinks.
Total water is not just drinks
The reference figure covers all water, including the part that comes from food, about 0.7 L for a man. That is why the drinks figure is lower than the total.
These are adequate-intake references for healthy adults, not a target that suits everyone.
Adding what you lose
Heat, exercise and illness raise fluid loss. The calculator adds the extra litres you enter to the drinks reference: for a man who loses 1 L more, that is 4.0 L of drinks.
Pregnancy, breastfeeding and your needs
Reference needs are higher during pregnancy (3.0 L of total water) and breastfeeding (3.8 L). Thirst, urine colour and medical conditions all matter, so ask a health professional for advice that fits you.
| Extra loss (L) | Adult man (L) | Adult woman (L) |
|---|---|---|
| 0 | 3.0 | 2.2 |
| 1 | 4.0 | 3.2 |
| 2 | 5.0 | 4.2 |
| 3 | 6.0 | 5.2 |
FAQ
Do I need exactly eight glasses a day?+
No. The eight-glass rule is a rough habit, and the reference figures count water from food as well as drinks.
Do coffee and tea count?+
Yes, they contribute to your fluid intake, as do other beverages.
Can I drink too much water?+
It is possible but rare. If you have a medical condition or take medication that affects fluids, ask a health professional.