In the first three months of life, a healthy baby gains about 1 ounce (28 grams) per day, which works out to roughly 1.5 to 2 pounds per month. That rate slows steadily as babies get older, dropping to about 1 to 1.25 pounds per month between 4 and 6 months, and slowing further in the second half of the first year. These are averages, and individual babies vary quite a bit week to week, but the overall trend on a growth chart matters more than any single weigh-in.
The First Two Weeks: Expect Some Weight Loss
Before your baby starts gaining, they’ll actually lose weight. Most newborns drop some of their birth weight in the first few days, then begin regaining it between days 3 and 5. About 80% of babies are back to their birth weight by 2 weeks of age. A loss of up to about 7% of birth weight is considered normal. If a newborn loses more than 10% of their birth weight or is slow to regain it, that’s a signal to evaluate feeding closely.
Weight Gain From Birth to 3 Months
Once feeding is established, the first three months are the fastest period of weight gain your baby will ever experience. At roughly an ounce per day, most babies put on 5 to 7 ounces per week during this stretch. Over a full month, that translates to about 1.5 to 2 pounds. Babies who were born small sometimes gain even faster as they “catch up,” while larger newborns may gain at the lower end of the range.
Growth isn’t perfectly smooth. Babies tend to have growth spurts at around 2 to 3 weeks and again at about 6 weeks. During these bursts, your baby may feed more frequently, seem fussier than usual, and sleep differently. A day or two of nonstop nursing or extra bottles is normal during a spurt and doesn’t mean your milk supply is low or that formula isn’t satisfying them.
Weight Gain From 4 to 6 Months
Growth starts to decelerate around 4 months. Babies at this age gain about 20 grams per day (compared to 28 grams in the early weeks), which adds up to roughly 1 to 1.25 pounds per month. By 4 to 5 months, most babies have doubled their birth weight. A baby born at 7.5 pounds, for example, would typically weigh around 15 pounds by the 5-month mark. Another growth spurt commonly hits around 3 months, with one more around 6 months.
Weight Gain From 6 to 12 Months
By 6 months, daily weight gain slows to about 10 grams or less per day. That works out to roughly half a pound to a pound per month, depending on the baby. This is completely normal and reflects the fact that babies are now channeling more energy into motor development, sitting up, crawling, and eventually pulling to stand. By their first birthday, most babies have tripled their birth weight. For that 7.5-pound newborn, that means landing somewhere around 22 to 23 pounds at 12 months.
Breastfed vs. Formula-Fed Growth Patterns
Breastfed and formula-fed babies don’t gain weight at exactly the same pace. In the first few months, their growth looks similar, but after about 3 months, formula-fed infants typically put on weight more quickly. Breastfed babies tend to be leaner through the first year, and this difference persists even after solid foods are introduced. Importantly, both groups grow at similar rates in length.
This distinction matters because the growth charts used in the U.S. for babies under 2 are the WHO charts, which are based on breastfed infants. The CDC specifically recommends these charts for children under 24 months because they treat the breastfed baby as the standard. If your pediatrician is using the WHO charts (as they should be for this age), a breastfed baby tracking along the 30th percentile is not “behind” a formula-fed baby at the 50th. They’re following different but equally healthy curves.
How Growth Charts Actually Work
Pediatricians don’t look at a single weight measurement in isolation. What they care about is the pattern over time. A baby who has been tracking along the 25th percentile and continues to do so is growing well, even though they’re smaller than 75% of babies their age. Percentiles describe where your baby falls relative to other babies, not whether they’re healthy or unhealthy.
What does raise concern is a baby who steadily drops from one percentile curve to a significantly lower one over multiple visits. This pattern of falling off the growth curve, sometimes called growth faltering, suggests a baby isn’t getting enough usable nutrition. There’s no single percentile that defines a problem. A baby consistently at the 5th percentile from birth is different from a baby who started at the 50th and dropped to the 5th.
Signs Your Baby May Not Be Gaining Enough
Between pediatric visits, there are a few things you can watch for. Babies who aren’t getting adequate nutrition may sleep more than expected or even fall asleep repeatedly during feedings. They may cry more than usual or seem less engaged, not mimicking facial expressions or interacting the way you’d expect for their age. Fewer wet and dirty diapers than normal can also be a signal, particularly in the early weeks when output is a reliable proxy for intake.
On the flip side, some parents worry about weight gain that seems too slow when it’s actually appropriate. A baby who is alert, feeding well, producing plenty of wet diapers, and meeting developmental milestones is almost certainly fine, even if their weight gain is on the lower end of average. The numbers in this article are guidelines, not rigid targets, and your baby’s overall trajectory matters far more than any single month’s gain.
Quick Reference by Age
- 0 to 3 months: about 1.5 to 2 pounds per month (5 to 7 ounces per week)
- 4 to 6 months: about 1 to 1.25 pounds per month
- 6 to 12 months: about 0.5 to 1 pound per month
- Double birth weight: around 4 to 5 months
- Triple birth weight: around 12 months