A two-week-old baby’s stomach holds roughly 2 to 3 ounces (60 to 90 milliliters) per feeding. That’s about the size of a large egg. It sounds tiny, and it is, but it’s already a dramatic expansion from birth, when the stomach could barely hold a teaspoon of milk.
How the Stomach Grows in the First Two Weeks
At birth, a newborn’s stomach capacity is just 5 to 7 milliliters, or about 1 to 1.5 teaspoons. It’s roughly the size of a cherry. The stomach walls are stiff and don’t stretch much, which is why those first colostrum feedings are so small.
By day three, capacity jumps to around 22 to 27 milliliters (about 4.5 to 5.5 teaspoons), closer to the size of a walnut. By day ten, the stomach can hold 60 to 81 milliliters, or 2 to 2.75 ounces. Between days 8 and 14, most babies hit their first growth spurt and start wanting to eat more frequently, which helps stretch the stomach further and signals the parent’s milk supply to increase.
By the end of week two into week three, the stomach comfortably holds 60 to 90 milliliters (2 to 3 ounces) per feeding. That’s roughly a tenfold increase from day one, happening in just 14 days.
What This Means for Feeding
Because the stomach is still so small at two weeks, babies need to eat frequently. Most breastfed newborns feed 8 to 12 times in 24 hours, or roughly every 2 to 4 hours. Formula-fed babies follow a similar pattern during this period, gradually working up to 3 to 4 ounces per feeding by the end of the first month.
A helpful rule of thumb from the American Academy of Pediatrics: babies generally need about 2.5 ounces of formula per day for every pound of body weight. So an 8-pound two-week-old would need around 20 ounces spread across the day. Breastfed babies take in similar total volumes, typically 20 to 25 ounces daily by the end of week three, though individual feedings vary more because breast milk flow isn’t as uniform as a bottle.
The stomach empties quickly at this age. In young infants, both breast milk and formula clear the stomach in well under an hour on average. This rapid emptying is another reason babies get hungry again so soon after eating. It’s not that they didn’t get enough; it’s that their digestive system processes milk fast and their stomach simply can’t store much at once.
Why Small Stomachs Lead to Spit-Up
Spitting up is one of the most common concerns parents have at this stage, and the small stomach is a big part of the reason. Newborns eat meals that are large relative to their body size compared to older children or adults. The muscle at the top of the stomach that keeps food down is also still immature. Together, these factors make it easy for stomach contents to come back up into the esophagus.
Occasional spit-up after feedings is normal and not a sign that something is wrong. It usually means the baby took in slightly more than the stomach could hold, or swallowed air during the feeding. Keeping the baby upright for 15 to 20 minutes after eating and using paced feeding techniques with a bottle can reduce how often it happens.
Signs of Overfeeding
Because a two-week-old’s stomach is only egg-sized, it’s possible to give more milk than the stomach can comfortably handle, especially with bottle feeding. Breastfed babies tend to self-regulate more easily since they control the flow. With a bottle, milk comes faster, and babies may continue sucking past the point of fullness simply because of the sucking reflex.
Common signs that feedings are too large include frequent forceful spit-up (not just small dribbles), visible discomfort or fussiness right after eating, and a hard, distended belly. If your baby seems unsettled after feedings, try offering slightly less volume more frequently rather than larger, spaced-out feedings. Matching the feeding size to what the stomach can actually hold, around 2 to 3 ounces at two weeks, keeps the baby more comfortable and reduces reflux.
How Quickly Stomach Size Keeps Growing
The rapid expansion seen in the first two weeks slows down after the first month. By four weeks, most babies take 3 to 4 ounces per feeding and settle into a more predictable schedule of eating every 3 to 4 hours. Total daily intake levels off at around 32 ounces for formula-fed babies, a ceiling that holds relatively steady through the first six months even as the baby gains weight. The stomach continues to grow, but feeding frequency gradually decreases to compensate, so total volume stays in the same range.