A 3-week-old typically eats 2 to 3 ounces per feeding, nursing or taking a bottle 8 to 12 times over a 24-hour period. That works out to roughly 16 to 24 total ounces per day, though every baby’s needs vary. The exact amount depends on whether your baby is breastfed, formula-fed, or both, and on how quickly they’re growing.
Ounces Per Feeding at Three Weeks
Between 1 and 3 weeks of age, most babies take 2 to 3 ounces at each feeding. By the time they pass the 3-week mark, that range shifts upward to about 3 to 5 ounces per feeding, according to guidance from the University of Iowa Health Care. This increase happens gradually, not overnight, so you may notice your baby draining bottles a little more completely or staying on the breast a bit longer as the weeks progress.
For formula-fed babies, the CDC recommends starting with 1 to 2 ounces every 2 to 3 hours in the earliest days, then increasing the amount as your baby shows signs of hunger. By three weeks, most formula-fed infants have settled into feedings of 2 to 3 ounces. If your baby consistently finishes the bottle and still seems hungry, it’s fine to add another half ounce or ounce and see if they want it.
Breastfed babies regulate their own intake at the breast, so you won’t be measuring ounces directly. Instead, you’ll rely on feeding frequency, diaper output, and weight gain to know they’re getting enough.
How Often to Feed
At this age, expect to feed your baby every 2 to 4 hours, which adds up to 8 to 12 feedings in 24 hours. Some of those feedings will cluster together, especially in the evening, with longer stretches (maybe 3 to 4 hours) at other times. This is normal. Babies generally take what they need at each feeding and stop when they’re full, so feeding on demand rather than on a rigid schedule is the most reliable approach.
Nighttime feedings are still essential at three weeks. Most babies this age are not ready to sleep through long stretches without eating, and skipping feeds can lead to underfeeding and slow weight gain.
The 3-Week Growth Spurt
Many babies hit a growth spurt right around 2 to 3 weeks old, and it can make feeding feel relentless. During a growth spurt, your baby may want to eat every 30 minutes, seem fussier than usual, and act unsatisfied even after a full feeding. This typically lasts only a few days.
If you’re breastfeeding, this frequent nursing is how your baby signals your body to produce more milk. It can feel like something is wrong, but the increased demand is temporary. For formula-fed babies, you may need to offer an extra ounce per bottle or add a feeding or two during the day. Once the spurt passes, your baby will likely settle back into a more predictable rhythm with slightly larger feeds than before.
How to Tell Your Baby Is Getting Enough
Since you can’t measure exactly how much a breastfed baby drinks, diaper output is the most practical way to check. At three weeks, a well-fed baby should produce at least 5 to 6 wet diapers and 3 to 4 or more soiled diapers every 24 hours. The stools should be at least the size of a quarter. For formula-fed babies, stool frequency can be slightly lower, but wet diaper counts should stay in the same range.
Steady weight gain is the other key indicator. Most pediatricians will weigh your baby at checkups and track their growth curve. Babies typically regain their birth weight by about 10 to 14 days old and then gain roughly 5 to 7 ounces per week through the first few months.
Reading Hunger and Fullness Cues
Rather than watching the clock, watch your baby. Early hunger cues include putting hands to the mouth, turning the head toward your breast or a bottle (called rooting), lip smacking, and clenched fists. These signals are your best window to start a feeding calmly. Crying is a late hunger sign, and a very upset baby can have trouble latching or settling into a feed.
Fullness looks different. A satisfied baby will close their mouth, turn away from the breast or bottle, and relax their hands. If your baby does this partway through a feeding, it’s fine to burp them and try offering more, but don’t force it. Pressuring a baby to finish a bottle can override their natural ability to self-regulate intake, which is one of the strongest protections against overfeeding in infancy.
Formula vs. Breastfed: Does the Amount Differ?
Breastfed and formula-fed babies end up consuming similar total volumes at this age, but the patterns can look different. Breastfed babies tend to eat smaller amounts more frequently because breast milk digests faster than formula. Formula-fed babies often go slightly longer between feeds and take a bit more per session.
If you’re doing a combination of both, there’s no single formula for splitting the amounts. Offer the breast first if you’re trying to maintain your milk supply, then top off with formula if your baby still seems hungry. Over time, you’ll get a sense of how much supplemental formula your baby needs per feeding.