The average 11-month-old boy weighs about 21.8 pounds (9.9 kg), while the average 11-month-old girl weighs about 19.2 pounds (8.7 kg). These are the 50th percentile values from the WHO growth standards, which means half of healthy babies weigh more and half weigh less. A wide range is completely normal, and your baby’s growth trend over time matters more than any single number on the scale.
Average Weight by Sex
Boys and girls follow slightly different growth curves, with boys typically running a pound or two heavier at this age. Here’s how the range breaks down using WHO growth chart percentiles:
Boys at 11 months:
- 5th percentile: 17.6 lbs (8.0 kg)
- 50th percentile: 21.8 lbs (9.9 kg)
- 95th percentile: 26.7 lbs (12.1 kg)
Girls at 11 months:
- 5th percentile: 15.9 lbs (7.2 kg)
- 50th percentile: 19.2 lbs (8.7 kg)
- 95th percentile: 23.6 lbs (10.7 kg)
That’s a spread of roughly 10 pounds between the lightest and heaviest healthy babies. A baby at the 15th percentile who has been tracking along that curve since birth is growing perfectly well. Percentiles aren’t grades. They simply show where your baby falls relative to other babies of the same age and sex.
How Fast Should Weight Change at This Age
Weight gain slows down significantly in the second half of the first year compared to the rapid gains of the first few months. At 10 to 12 months, babies gain an average of about 13 ounces per month, or roughly 3 ounces per week. That’s a fraction of the pace during the newborn period, and it’s perfectly normal. Many parents notice the slowdown and worry, but this deceleration is expected as babies become more mobile and shift more energy toward activity.
What pediatricians look for isn’t a specific weekly number but a consistent pattern. A baby who drops across two major percentile lines on the growth chart (say, from the 50th to the 10th) warrants a closer look. Weight falling below the 3rd or 5th percentile, or a noticeable downward shift in the growth curve, is the clinical threshold for concern about inadequate growth. Steady tracking along any percentile, even a low one, is reassuring.
Why Some 11-Month-Olds Weigh More or Less
Genetics is the biggest driver. Tall parents tend to have longer, heavier babies. Shorter parents tend to have smaller ones. Birth weight also plays a role: babies born larger tend to stay on the heavier side, and research suggests higher birth weight raises the risk of carrying extra weight into childhood. Gestational diabetes during pregnancy can increase birth weight as well.
Feeding method matters too. Breastfed babies and formula-fed babies follow slightly different growth patterns. Breastfed infants often gain weight faster in the first three months, then more slowly afterward compared to formula-fed babies. This is one reason the WHO growth charts are recommended for all children under 2: they’re based on breastfed infants as the standard, reflecting optimal growth rather than just average growth in a specific population.
Activity level is another factor. At 11 months, most babies are crawling, pulling to stand, or cruising along furniture. Research from Johns Hopkins found that more physically active infants had less fat accumulation around their midsection. Babies who start crawling and walking earlier tend to burn more calories, which can slow the rate of weight gain slightly. Providing plenty of floor time and opportunities for free movement supports a healthy body composition.
Sleep also has a measurable impact. Babies who get enough sleep are more likely to maintain a healthy weight, while increased screen time, even at this young age, is associated with a greater risk of becoming overweight.
Feeding for Healthy Growth at 11 Months
Breast milk or formula is still the primary source of nutrition at 11 months, but solid foods are playing an increasingly important role. By this age, your baby should be eating something every two to three hours, which works out to about three meals and two to three snacks per day. That rhythm supports steady growth without overfeeding.
Portion sizes stay small. Starting with one or two tablespoons of a food and watching your baby’s hunger and fullness cues is the recommended approach. Some babies eat quickly and don’t register when they’re full, so pacing meals and letting your baby self-feed when possible helps them learn to stop when satisfied. Over the coming weeks, the balance will gradually tip further toward solids as your baby approaches the one-year mark.
Which Growth Chart Your Doctor Uses
The CDC recommends using WHO growth charts for all children under 24 months, regardless of whether they’re breastfed or formula-fed. The WHO charts represent how healthy children should grow under optimal conditions, while the older CDC charts describe how a specific group of American children actually grew, including those who were formula-fed or had other variables. The practical difference: CDC charts tend to flag more babies as underweight (7 to 11 percent of 6- to 23-month-olds) compared to the WHO charts (under 3 percent). The CDC charts also identify more infants under 12 months as overweight (9 to 13 percent versus 5 to 9 percent on the WHO charts).
If you’re comparing your baby’s weight to a chart you found online, make sure it’s a WHO chart. Using the wrong reference can make a perfectly healthy baby look too heavy or too light, which creates unnecessary worry.