The average 1-year-old weighs about 20 pounds (9.0 kg). Boys tend to be slightly heavier than girls at this age, but most healthy 12-month-olds fall somewhere between 18 and 25 pounds (8.1 to 11.5 kg). That range covers the 5th to 95th percentiles on the World Health Organization growth charts, meaning the vast majority of one-year-olds land within it.
Boys vs. Girls at 12 Months
Boys at 12 months typically weigh a bit more than girls. On the WHO growth charts, the 50th percentile for boys is roughly 9.6 kg (21.2 lbs), while the 5th percentile is 8.1 kg (17.9 lbs) and the 95th is 11.5 kg (25.4 lbs). Girls follow a similar pattern shifted slightly lower, with a 50th percentile around 8.9 kg (19.6 lbs).
These numbers come from the WHO international growth standard, which was developed in 2006 by tracking children in six countries who were raised in conditions supporting optimal growth, including breastfeeding. The CDC recommends using the WHO charts for all children under age 2, regardless of how they’re fed.
How This Compares to Birth Weight
Most babies triple their birth weight by their first birthday. A baby born at 7.5 pounds would be expected to weigh roughly 22 to 23 pounds at 12 months. If your baby was born smaller or larger than average, their one-year weight will naturally reflect that starting point. What matters more than hitting a specific number is whether the growth curve has been consistent over time.
Breastfed vs. Formula-Fed Babies
Growth patterns differ depending on how a baby is fed. Breastfed infants typically put on weight more slowly than formula-fed infants during the first year. Formula-fed babies tend to gain weight more quickly after about 3 months of age, and those differences persist even after solid foods are introduced. Both patterns are normal. Height growth, by contrast, is similar regardless of feeding method.
This distinction matters because a breastfed baby who tracks along the 25th percentile isn’t necessarily underweight. Older growth charts were based largely on formula-fed infants, which could make a healthy breastfed baby look like they were falling behind. The WHO charts correct for this.
What the Percentiles Actually Mean
A percentile tells you how your child’s weight compares to other children of the same age and sex. A baby at the 40th percentile weighs more than 40% of babies and less than 60%. Being at the 15th percentile doesn’t mean something is wrong. It means your child is on the lighter side, and that’s fine as long as they’ve been tracking consistently along that curve.
The number that raises concern isn’t a single low percentile. It’s a drop across two or more major percentile lines over time. For example, a baby who was at the 75th percentile at 6 months and falls to the 25th percentile by 12 months warrants a closer look. Sustained drops like this are one of the clinical markers for failure to thrive, a term used when a child’s weight falls below the 5th percentile or their growth velocity slows significantly. Weight below the 5th percentile on its own can also prompt evaluation, though some small babies are simply genetically small.
What to Expect After the First Birthday
Growth slows dramatically in the second year. During infancy, your baby may have gained 4 pounds in as little as four months. During the entire second year, most toddlers gain only 3 to 5 pounds total. This slowdown is completely normal and often coincides with a dip in appetite that catches parents off guard. Toddlers become more mobile, more opinionated about food, and less interested in sitting still for meals. Their growth rate simply doesn’t demand the same caloric intake it once did.
How to Get an Accurate Weight at Home
If you want to track your child’s weight between checkups, a few details make the reading more reliable. Use a digital scale rather than a spring-loaded bathroom scale. Place it on a hard, flat surface like tile or wood, not carpet. Have your child stand with both feet centered on the scale (if they can stand steadily), wearing only a diaper or light clothing and no shoes. Record the weight to the nearest decimal, like 21.3 pounds, so you can spot trends over time.
For a one-year-old who can’t stand still on a scale, you can step on the scale alone, note your weight, then step on again holding your child. The difference gives you a reasonable estimate, though your pediatrician’s infant scale will be more precise.