Most newborns gain about 1 ounce per day, or roughly 5 to 7 ounces per week, during their first few months of life. That rate slows steadily as babies get older, dropping to about half that pace by 4 months and slowing further after 6 months. These are averages, and healthy babies can fall above or below them, so the overall trend on a growth chart matters more than any single weekly number.
Weight Gain From Birth to 3 Months
The first three months are a baby’s fastest period of growth. After an initial dip in the first few days (most newborns lose 5 to 10 percent of their birth weight before regaining it by about two weeks), babies typically gain around 1 ounce per day. That works out to roughly 5 to 7 ounces per week, or close to 1.5 to 2 pounds per month.
This early stretch can feel dramatic. A baby born at 7.5 pounds might weigh over 10 pounds by the time they hit the 6-week mark. If your baby regains their birth weight by about two weeks and continues climbing steadily from there, that’s a strong sign feeding is going well.
Weight Gain From 3 to 6 Months
Growth starts to taper around 4 months. Babies at this stage gain closer to 4 to 5 ounces per week, or about 20 grams per day. Boston Children’s Hospital flags daily gains below about two-thirds of an ounce (roughly 0.67 ounces) as a potential concern for babies between 3 and 6 months, so that’s a useful lower boundary to keep in mind.
By 6 months, a healthy baby has typically doubled their birth weight. A baby born at 7 pounds, for example, would be expected to weigh around 14 pounds by this point. This doubling milestone is one of the simplest benchmarks pediatricians use to check that growth is on track.
Weight Gain From 6 to 12 Months
After 6 months, weight gain slows further to roughly 2 to 3 ounces per week, or about 10 grams per day. Babies are more mobile now, crawling, pulling up, and eventually cruising, which burns more energy and naturally slows the rate of gain. The introduction of solid foods also changes the equation, though breast milk or formula still provides most of a baby’s calories through the first year.
By their first birthday, most babies have tripled their birth weight. That 7-pound newborn is now around 21 pounds. Some babies hit this mark a little before 12 months, others a little after, and both are perfectly normal as long as the growth curve stays consistent.
Breastfed vs. Formula-Fed Growth Patterns
Breastfed and formula-fed babies grow at different rates, and this is completely normal. In the early weeks, their weight gain looks similar. After about 3 months, formula-fed babies typically gain weight faster. Breastfed babies tend to be leaner through the first year, even after starting solid foods. Their length growth, however, is virtually identical regardless of feeding method.
This distinction matters because of how growth charts work. The older CDC growth charts were built primarily from data on formula-fed infants, which can make a healthy breastfed baby look like they’re falling behind. That’s why the CDC now recommends using the World Health Organization (WHO) growth charts for all children under 2 years old. The WHO charts treat breastfeeding as the biological norm, so they reflect what healthy breastfed growth actually looks like. If your pediatrician is using the WHO charts (most do for babies under 24 months), a breastfed baby who dips slightly on their percentile curve isn’t necessarily a concern.
What Growth Charts Actually Tell You
Pediatricians track four main measurements: weight for age, length for age, weight for length, and head circumference. No single weigh-in tells you much on its own. What matters is the pattern over multiple visits. A baby who has consistently been in the 25th percentile is growing normally for their body. A baby who drops from the 60th percentile to the 15th percentile over two or three visits is the one who needs closer attention, even if their actual weight looks fine in isolation.
Percentiles describe where your baby falls compared to other babies of the same age and sex. A baby in the 40th percentile weighs more than 40 percent of babies their age and less than 60 percent. There is no “ideal” percentile. Babies at the 10th and 90th percentile can both be perfectly healthy. The key question is whether your baby is following their own curve consistently.
Signs Your Baby Is Getting Enough
Between pediatrician visits, the easiest way to gauge adequate feeding is diaper output. By day 5 of life, a breastfed baby should be producing at least 6 wet diapers per day. Fewer than that in the early weeks can signal insufficient intake. Stool frequency varies more widely, especially after the first month, so wet diapers are the more reliable marker.
Other reassuring signs include a baby who seems satisfied after feeding, has good skin tone, is alert during wake periods, and is meeting developmental milestones. Fussiness alone isn’t a reliable indicator that a baby isn’t eating enough, since babies fuss for dozens of reasons unrelated to hunger.
When Weight Gain Is Too Slow
The clinical term for persistently poor weight gain is “failure to thrive,” though many pediatricians now avoid that phrase because it sounds more alarming than it needs to be. It’s not a diagnosis. It’s a description of a pattern: a baby who isn’t gaining enough weight over time. The American Academy of Family Physicians emphasizes that it requires multiple weight measurements showing an inadequate trend, not a single low number.
Causes range from simple and fixable (a poor latch during breastfeeding, not feeding frequently enough, an undiagnosed tongue tie) to medical issues that need workup (food allergies, reflux, metabolic conditions). In most cases, the fix is straightforward once the underlying issue is identified. If your baby’s pediatrician flags slow weight gain, they’ll typically start by reviewing feeding patterns and adjusting from there before pursuing more involved testing.
A Quick Reference by Age
- Birth to 3 months: about 5 to 7 ounces per week (1 ounce per day)
- 3 to 6 months: about 4 to 5 ounces per week (roughly 0.7 ounces per day)
- 6 to 12 months: about 2 to 3 ounces per week (roughly 0.35 ounces per day)
- By 6 months: most babies double their birth weight
- By 12 months: most babies triple their birth weight