The average 10-month-old boy weighs about 20.2 pounds, and the average 10-month-old girl weighs about 18.7 pounds. But “average” is just the midpoint. A healthy 10-month-old can weigh anywhere from about 16 to 24 pounds depending on sex, genetics, and feeding patterns. What matters more than hitting a specific number is whether your baby is growing consistently along their own curve.
Average Weight by Sex
Growth charts from the CDC and the World Health Organization break infant weight into percentiles, with the 50th percentile representing the statistical middle. At 10 months, those midpoints look like this:
- Boys: about 20.2 pounds at the 50th percentile, with a typical range of roughly 17.6 pounds (5th percentile) to 23.5 pounds (95th percentile)
- Girls: about 18.7 pounds at the 50th percentile, with a typical range of roughly 16 pounds (5th percentile) to 22 pounds (95th percentile)
A baby sitting at the 15th percentile is not underweight in any clinical sense. Percentiles describe where a baby falls relative to other babies the same age and sex. A baby who has tracked along the 15th percentile since birth is growing exactly as expected for their body. The same applies to babies at the 85th or 90th percentile.
How Fast Weight Gain Slows Down
Babies gain weight fastest in the first few months of life, then the pace gradually tapers. Between 10 and 12 months, the typical baby gains about 13 ounces per month, roughly a third of what they gained each month during the newborn period. By their first birthday, most babies have tripled their birth weight. So a baby born at 7.5 pounds would be expected to weigh somewhere around 22 to 23 pounds at 12 months.
This slowdown is completely normal and partly reflects the fact that 10-month-olds are burning far more calories than they used to. Most babies this age are crawling, pulling to stand, or cruising along furniture. All that movement uses energy that previously went straight toward gaining weight.
Breastfed vs. Formula-Fed Differences
Breastfed babies and formula-fed babies follow noticeably different weight trajectories during the first year. Breastfed infants typically put on weight more slowly than formula-fed infants, especially after about 3 months of age. This difference persists even after babies start eating solid foods. It does not mean breastfed babies are underfed. Their growth in length is similar to formula-fed babies; the difference is primarily in weight gain.
The CDC recommends using WHO growth charts for all infants under 2, regardless of feeding method, because the WHO charts were built from data on breastfed babies and better reflect healthy growth patterns. If your pediatrician’s office is using CDC charts for an infant under 2, it can sometimes make a normally growing breastfed baby look like they’re falling behind when they aren’t.
What Your Baby Needs to Eat at This Age
A 10-month-old needs roughly 750 to 900 calories per day. About 400 to 500 of those calories should still come from breast milk or formula, which works out to around 24 ounces a day. The rest comes from solid foods. At this age, most babies are eating three small meals a day with one or two snacks, gradually working toward a more table-food-based diet.
This transition period can sometimes cause temporary dips in weight gain. Some babies are so enthusiastic about solid foods that they drink less milk, while others are slow to warm up to solids and may not be getting enough calories from food yet. Neither pattern is unusual, but both are worth mentioning to your pediatrician if weight gain stalls for more than a few weeks.
When a Weight Change Is Worth Watching
Pediatricians don’t worry about a single low (or high) weight reading. They look at the trend over time. The real red flag is when a baby’s growth curve crosses two or more percentile lines on the chart. For example, a baby who was tracking above the 75th percentile and drops below the 25th percentile over several months warrants investigation. This kind of persistent downward trend, usually lasting many months, is what clinicians consider a sign of inadequate nutrition or an underlying health issue.
A baby who has always tracked below the 5th percentile but follows that line steadily is growing at a normal rate for their body. A baby who was at the 50th percentile and suddenly drops to the 5th is in a very different situation, even though they may weigh more than the first baby. The pattern matters more than the number.
Short-term fluctuations are common and usually harmless. A stomach bug, a week of teething pain that disrupts eating, or a growth spurt that temporarily changes the ratio of weight to length can all shift a baby’s position on the chart briefly. These blips tend to correct themselves within a few weeks.
Factors That Shape Your Baby’s Size
Genetics is the single biggest driver of where your baby lands on the growth chart. Tall, large-framed parents tend to have bigger babies, and smaller parents tend to have smaller ones. Premature babies often track lower on standard growth charts for the first year or two before catching up, and their pediatricians typically use adjusted age when plotting growth.
Activity level also plays a role at this age. Research from the University of North Carolina found that overweight infants were about 1.8 times more likely than non-overweight infants to show delayed motor development, meaning they were slower to crawl and walk. Babies who are very active and mobile tend to lean out as they burn more calories, while less mobile babies may carry more weight. Neither pattern is automatically a concern, but the relationship between weight and movement is worth keeping in mind.
Birth weight sets the starting point but doesn’t lock in a baby’s trajectory. Some babies born small experience “catch-up growth” in the first few months and settle into a higher percentile. Others born large gradually shift downward toward a percentile that better matches their genetic blueprint. These early adjustments are normal and typically happen in the first six months, so by 10 months most babies have found the curve they’ll follow for the rest of infancy.