In the first three months of life, babies typically gain about 1.5 to 2 pounds per month. That rate gradually slows as the year goes on, dropping to about 1 to 1.25 pounds per month between four and six months, and slowing further in the second half of the year. By six months, most babies have doubled their birth weight, and by their first birthday, they’ve tripled it.
The First Two Weeks: Weight Loss Before Gain
Before any weight gain happens, newborns actually lose weight. Healthy babies drop 7 to 10 percent of their birth weight in the first few days as their mother’s milk supply is being established and they’re shedding extra fluid from the womb. A baby born at 7.5 pounds might dip to around 6 pounds 12 ounces before the scale starts climbing again. Most babies regain their birth weight by two weeks of age, and from that point forward, the gains come fast.
Birth to Three Months
This is the fastest growth period. Babies gain roughly 1.5 to 2 pounds each month, which works out to about an ounce a day. In grams, that’s approximately 26 to 31 grams daily. It’s common for newborns to seem like they’re outgrowing clothes and diapers almost weekly during this stretch, and that pace is completely normal.
Four to Six Months
Growth starts to decelerate slightly. The average baby gains about 1 to 1.25 pounds per month during this window, or roughly 17 to 18 grams per day. While the numbers are smaller than the newborn period, the gains are steady. Most babies hit double their birth weight somewhere around the six-month mark. A baby born at 7 pounds, for instance, will typically weigh around 14 pounds by half a year.
Seven to Twelve Months
Weight gain continues to taper as babies become more mobile. Between six and nine months, daily gains average about 12 to 13 grams, which translates to roughly half a pound to three-quarters of a pound per month. From nine to twelve months, that slows further to about 9 grams per day. By a baby’s first birthday, most have tripled their birth weight, landing somewhere in the 20 to 23 pound range for an average-sized newborn.
Breastfed vs. Formula-Fed Growth
Breastfed and formula-fed babies don’t gain weight at the same pace. In the first three months, the two groups look similar, but after that, formula-fed babies typically gain weight more quickly. Breastfed infants put on weight more slowly throughout their first year overall, and this difference persists even after solid foods are introduced. Both patterns are normal. Length (height) growth is similar regardless of feeding method.
This distinction matters because growth charts based on formula-fed babies can make a breastfed infant look like they’re falling behind when they’re actually growing appropriately. The World Health Organization growth charts are based on breastfed infants and give a more accurate picture for babies who are nursing.
Signs That Growth May Be Off Track
Individual babies vary, and a single weigh-in that seems low isn’t usually a concern on its own. What pediatricians watch for is a pattern: weight dropping below the 5th percentile for age and sex, or weight crossing downward across two major percentile lines on a growth chart over time. A baby who has been tracking along the 50th percentile and suddenly drops to the 10th, for example, would warrant a closer look even though the 10th percentile is still within normal range.
In practical terms, a newborn gaining noticeably less than an ounce a day in the first three months, or a baby who hasn’t regained birth weight by two to three weeks, is worth discussing with a pediatrician. Slow gain often comes down to feeding difficulties that are straightforward to address, like latch problems, insufficient milk transfer, or not feeding frequently enough.
Month-by-Month Weight Gain at a Glance
- 0 to 3 months: 1.5 to 2 pounds per month (26 to 31 grams per day)
- 3 to 6 months: 1 to 1.25 pounds per month (17 to 18 grams per day)
- 6 to 9 months: 0.5 to 0.75 pounds per month (12 to 13 grams per day)
- 9 to 12 months: about 0.5 pounds per month (roughly 9 grams per day)
These are averages across healthy infants. A baby who falls slightly above or below these ranges but follows a consistent curve on their growth chart is typically growing just fine. What matters most is the trajectory over time, not any single month’s number.