Your Baby’s First 6 Months, by the Numbers

your baby's first 6 months

Watching your baby grow and develop new skills is one of the joys of being a parent. Your baby’s first 6 months are especially jam-packed with milestones and exciting transitions. If you’re a first-time parent, you might not know what to expect during this busy season of babyhood. Seasoned moms tend to compare new babies with older siblings, and we’re all guilty of looking at other babies and wondering, “Why isn’t my baby doing that yet?” We’ve researched a few stats and facts on the average baby for an unbiased look at what to anticipate in those first few months.


  • In the United States, the average newborn baby weighs 7 pounds, 7.8 ounces. The average newborn baby girl weighs about 7 pounds, while the average baby boy weighs nearly 8 pounds. By six months, the average baby boy weighs between 17 and 18 pounds, and is 27 inches long. At the same age, the average baby girl weighs about 16 pounds and is 26 inches long.1
  • The CDC growth charts for boys and girls also show that babies grow about an inch a month for the first six months, with the exception of the second month of life. Then, little ones can shoot up an average of two whole inches; that’s half an inch each week!
  • Breastfeeding? Breastfed babies tend to double their birth weight before they are four months old. By six months, exclusively breastfed babies will generally weigh above the 50th percentile2 (16 to 20 pounds for girls3, and 18 to 22 pounds for boys4).


  • Does it seem like your baby is constantly hungry? He or she probably is! Babies under three months of age eat an average of six to seven times per day at 2- or 3-hour intervals. At night, these youngsters tend to eat at 4- to 6-hour intervals5.
  • Breastfeeding moms may be dismayed at the number of times they’re changing poopy diapers, but this will decrease significantly in the first three months (from an average of 3.65 to 1.88 dirty diapers a day). Formula-fed babies poop less frequently than breastfed babies, and their stools tend to be greener and harder6.
  • 81.1% of babies are breastfed at some point in their lives. 44.4% of women are still exclusively breastfeeding their babies at three months, and 22.3% follow the World Health Organization’s recommendation of breastfeeding exclusively until at least six months. About half of all moms are still breastfeeding when their babies are six months old, even if they’re also using food or formula to supplement7.


  • According to one study, three-month-olds sleep an average of almost 13 hours, including about 3 hours and 20 minutes of naps during the day. By six months, that same study found that the average baby sleeps almost 10 hours at night and only wakes up an average of 1.5 times8. So if you’re struggling with nighttime feedings, hang in there, parents! Sleep time varies the most before a baby is six months old, but by the time babies reach that critical age, those very vocal wakeups tend to be less frequent5.
  • Another study found that 35% of babies under three months slept through the night; by 9-12 months of age, 72% were sleeping for six-hour stretches9. (Of course, most of us don’t really consider a six-hour stretch to be “continuous nighttime sleep,” but we’ll take what we can get!).


  • About half of all babies can sit without support at six months. 10% can stand with assistance, and 5% can crawl on their hands and knees10. Help your baby by giving him or her lots of tummy time and by offering gentle support as he or she sits and stands, and your little one will be well on the way to reaching these milestones!
  • Between three and six months, most babies establish a predictable sleeping and eating schedule. Around three or four months, your baby will start anticipating a routine11. If it feels like random feedings and sporadic naps will never end, know that you will soon be able to actually have a schedule again soon!

Don’t worry if your little one doesn’t fit these stats exactly. These are only averages, and every baby is unique in his or her developments and behaviors. If you have any questions about your baby’s milestones and growth, your health care provider will be able to clarify any concerns or provide more information. First and foremost, remember to enjoy how precious baby’s first 6 months of exciting growth. They will fly by!

Wondering what to expect beyond 6 months?  Sign up for an upcoming Your Older Baby class to learn the 6-12 month milestones, introducing solids, baby sign language, and more.

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