Most 10-month-old boys weigh between 17.5 and 22 pounds, while most girls weigh between 16 and 20.5 pounds. Those ranges cover the 25th to 75th percentiles on the World Health Organization growth charts, which pediatricians in the United States use for all children under 2. But a single weight reading matters far less than your baby’s overall growth pattern over time.
Average Weight by Sex
The WHO growth standards place the 50th percentile for 10-month-old boys at roughly 20 pounds and for girls at about 18.5 pounds. Babies who fall anywhere between the 5th and 95th percentiles are generally considered within a healthy range, so there’s a wide spread of normal. A 10-month-old girl weighing 15 pounds can be perfectly healthy if she’s been tracking along her own curve since birth, just as a boy weighing 24 pounds can be fine if that’s consistent with his growth trajectory.
What pediatricians care about most is the pattern. They plot your baby’s weight at each visit and look at how the dots connect. A baby who has been near the 20th percentile since birth and stays there is growing well. A baby who was at the 60th percentile and has dropped to the 15th over a few months raises more questions, even if that lower number is technically “normal.”
How Fast Weight Gain Slows Down
Weight gain at 10 months is considerably slower than it was in those early months. Between 10 and 12 months, babies gain an average of about 13 ounces per month, according to Children’s Hospital of Philadelphia. Compare that to the first few months of life, when many infants pack on 5 to 7 ounces per week.
This slowdown is completely expected. Babies are burning more calories now because they’re crawling, pulling up, cruising along furniture, and possibly taking early steps. That increased mobility means some babies actually thin out a bit, losing their round baby look as they stretch and move more. If your baby seems to have plateaued or gained less weight than previous months, increased activity is often the reason.
Breastfed vs. Formula-Fed Babies
Breastfed and formula-fed babies follow slightly different weight trajectories. Healthy breastfed infants typically gain weight more slowly than formula-fed infants after about 3 months of age, and those differences persist even after solid foods enter the picture. This is why the CDC and American Academy of Pediatrics recommend using the WHO growth charts for all children under 2. The WHO charts were built from data on breastfed babies and reflect that slightly leaner growth pattern as normal rather than a concern.
If your breastfed 10-month-old weighs less than a formula-fed baby the same age, that alone isn’t a red flag. It’s a predictable difference in how the two groups grow.
What Premature Babies Should Weigh
If your baby was born early, the standard 10-month benchmarks don’t apply directly. Pediatricians use “corrected age” instead, which adjusts for how early your baby arrived. To calculate it, subtract the number of weeks your baby was premature from their actual age. A baby born at 34 weeks (6 weeks early) who is now 10 months old has a corrected age of about 8.5 months, and their weight should be compared to the growth chart values for that corrected age.
Most doctors continue using corrected age for growth assessments until a child is about 2 years old. Premature babies typically close the gap with their full-term peers over time, but expecting them to hit the same weight milestones at the same calendar age creates unnecessary worry.
Feeding and Its Effect on Weight
At 10 months, breast milk or formula is still the primary source of nutrition, but solid foods are playing an increasingly important role. The CDC recommends offering something to eat or drink about every 2 to 3 hours, which works out to roughly 3 meals and 2 to 3 snacks per day. Start with small portions of 1 to 2 tablespoons and watch for your baby’s hunger and fullness cues.
Babies who resist solids or who have recently been sick may gain weight more slowly for a stretch. On the other hand, babies who take enthusiastically to table food while still drinking the same amount of breast milk or formula may gain a bit faster. Neither pattern is inherently concerning unless it persists long enough to shift the growth curve.
Signs of a Weight Problem
Pediatricians look for what’s called “failure to thrive” when a baby’s weight gain velocity drops and they steadily fall off their expected growth curve. This isn’t diagnosed from a single weigh-in. It requires reliable, repeated measurements over time, plotted on the appropriate growth chart. A baby who crosses downward across two or more major percentile lines (for example, dropping from the 50th to below the 10th) will typically prompt further evaluation.
On the flip side, rapid upward crossing of percentile lines can also warrant a closer look, though it’s less commonly flagged at this age.
Some practical things to watch for at home: your baby seems consistently unsatisfied after feedings, has fewer than 4 wet diapers a day, appears lethargic or unusually irritable, or seems to be losing skills they previously had. These warrant a conversation with your pediatrician sooner than the next scheduled visit.
Getting an Accurate Weight
If you’re weighing your baby at home and comparing to growth charts, keep in mind that clinical measurements follow a specific protocol. In a pediatric office, infants are weighed in just a dry diaper or undergarments, on a calibrated scale. Clothing, a full diaper, or a different scale can easily add half a pound or more, which is enough to shift a percentile reading at this age. For the most reliable tracking, use the weights recorded at your baby’s well-child visits rather than home measurements.