A 3-week-old baby typically drinks 2 to 3 ounces (60 to 90 mL) per feeding, eating 8 to 10 times over a 24-hour period. That works out to roughly 16 to 24 ounces of breast milk or formula per day, though the exact amount varies from baby to baby and even from feeding to feeding.
How Much Per Feeding at 3 Weeks
At 3 weeks old, your baby’s stomach can hold about 2 to 3 ounces at a time. That’s a significant jump from the first few days of life, when a newborn’s stomach holds barely a teaspoon, but it’s still quite small. Most babies at this age settle into a pattern of taking 2 to 3 ounces per bottle or per breastfeeding session. By the time your baby reaches one month, that amount will increase to 3 to 4 ounces per feeding.
The amount can vary depending on your baby’s weight and whether they’re in the middle of a growth spurt. A 3-week-old who weighs more than average may consistently take closer to 3 ounces, while a smaller baby might be satisfied with 2. Your baby’s appetite will also shift throughout the day. Some feedings will be bigger, others smaller. That’s normal.
How Often to Feed
Expect to feed your 3-week-old every 2 to 3 hours, which adds up to about 8 to 10 feedings in 24 hours. Breastfed babies sometimes eat even more frequently, up to 12 times a day, because breast milk digests faster than formula. This means you’ll likely be feeding during the night as well. At this age, babies should not go long stretches without eating, even overnight.
The timing is measured from the start of one feeding to the start of the next. So if your baby starts eating at 6:00 a.m. and takes 30 minutes, the next feeding would begin around 8:00 or 8:30 a.m.
Breastfed vs. Formula-Fed Babies
If you’re breastfeeding, you can’t measure exactly how many ounces your baby takes at each session, which can feel stressful. The good news is that breastfed babies are naturally good at regulating their intake. They’ll pull away or stop sucking when they’ve had enough. As long as your baby is feeding 8 to 12 times per day and showing signs of satisfaction afterward (relaxed hands, turning away from the breast), they’re almost certainly getting what they need.
Formula-fed babies are easier to track by volume. At 3 weeks, offer 2 to 3 ounces per bottle. If your baby finishes the bottle quickly and still seems hungry, it’s fine to prepare a small additional amount. But resist the urge to encourage your baby to finish every last drop. If they stop feeding or lose interest, the feeding is done.
How to Tell Your Baby Is Getting Enough
Diapers are your best daily indicator. After the first week of life, your baby should produce at least 6 wet diapers per day. The number of soiled (poopy) diapers varies more widely, but breastfed babies at this age often have several per day. Fewer than 6 wet diapers in a 24-hour period can signal that your baby isn’t getting enough milk.
Weight gain is the other reliable measure. In the first 3 months, babies typically gain about 150 to 200 grams (5 to 7 ounces) per week. Your pediatrician will track this at well-baby visits. Most babies lose some weight in the first few days after birth and then regain it by about 10 to 14 days old. By 3 weeks, your baby should be at or above their birth weight and gaining steadily.
Reading Your Baby’s Hunger Cues
Rather than watching the clock, it helps to learn the early signs that your baby is ready to eat. At this age, hunger cues include putting hands to their mouth, turning their head toward your breast or a bottle (called rooting), puckering or smacking their lips, and clenching their fists. Crying is actually a late sign of hunger. If you wait until your baby is crying hard, they may be too upset to latch or feed well, so try to catch those earlier signals.
Fullness cues are just as important. A satisfied baby will close their mouth, turn their head away from the breast or bottle, and visibly relax their hands. These signs mean the feeding is over, even if the bottle isn’t empty or the session was shorter than usual.
Signs Your Baby May Need More
Growth spurts are common around 2 to 3 weeks and again around 6 weeks. During a spurt, your baby may want to eat more frequently for a day or two. This is called cluster feeding and is especially common in breastfed babies. It can feel relentless, but it typically resolves within 24 to 48 hours. Following your baby’s lead and feeding on demand during these periods helps ensure they get the extra calories they need.
If your baby consistently seems unsatisfied after feedings, isn’t producing enough wet diapers, or isn’t gaining weight at their checkups, those are signs that feeding may need to be adjusted. This could mean more frequent feedings, checking your breastfeeding latch, or discussing formula supplementation with your pediatrician.