Most breastfeeding parents need roughly 13 cups (about 3.1 liters, or 100 ounces) of total fluids per day, according to general guidance from bodies like the U.S. National Academies of Sciences. This is more than the roughly 9 cups recommended for non-lactating adults, since milk production draws on the body's water supply — breast milk itself is about 87% water. This total fluid figure includes water from all beverages (milk, juice, tea) as well as water-rich foods like fruits and soups, not just plain water from a glass.
A simple and widely used practical strategy is to drink a glass of water every time you nurse or pump, since feeding sessions naturally cue you to hydrate throughout the day. Thirst is generally a reliable guide — many nursing parents notice they feel thirstier than usual, especially right at the start of a feeding, and responding to that cue is usually enough to stay adequately hydrated.
Individual needs vary based on climate, activity level, body size, how much you're sweating, and how much milk you're producing (for example, needs are higher for those nursing twins or exclusively pumping large volumes). Signs of adequate hydration include pale yellow urine, regular urination, and not feeling excessively thirsty; dark urine, dry mouth, dizziness, or reduced milk supply can signal you need more fluids.
Contrary to a common myth, drinking large amounts beyond thirst does not meaningfully boost milk supply — supply is driven mainly by how often and effectively milk is removed from the breast. However, becoming significantly dehydrated can reduce supply and cause fatigue, headaches, or constipation, so consistent, moderate hydration throughout the day is more useful than trying to force extra water in one sitting. Caffeinated and alcoholic beverages count toward fluid intake but should be limited, as they can affect the baby through breast milk. If you have specific health conditions or concerns about supply, a lactation consultant or healthcare provider can offer personalized guidance.