The average weight of a one-year-old is about 22 pounds (10 kg) for boys and 20 pounds (9.2 kg) for girls. Most babies triple their birth weight by their first birthday, so a baby born at a typical 7 to 7.5 pounds will land right around these numbers. That said, healthy one-year-olds can vary quite a bit, and where your child falls on the growth chart matters more than hitting one specific number.
Average Weight by Sex
Boys and girls follow slightly different growth curves from birth onward. The average full-term boy is born at about 7 pounds 6 ounces, while the average girl is born at 7 pounds 2 ounces. By 12 months, that gap widens a little. Boys typically weigh between 19.5 and 24.5 pounds, while girls typically fall between 18 and 23 pounds. These ranges represent roughly the 15th to 85th percentiles on standard growth charts.
The tripling rule is a useful shortcut. If your baby was born at 6 pounds, a weight near 18 pounds at one year is perfectly normal, even though it’s below the “average.” A baby born at 8.5 pounds might weigh 25 or 26 pounds and still be right on track. Your pediatrician tracks growth over time on a percentile curve, and consistency along that curve is more meaningful than any single number.
What Affects Weight at One Year
Birth weight is the biggest starting variable. Babies born premature or small for gestational age often follow adjusted growth curves for the first year or two. A baby born at 34 weeks, for example, may not hit the same milestones on the same calendar timeline as a full-term baby, and that’s expected.
Feeding method also plays a role. Healthy breastfed infants typically put on weight more slowly than formula-fed infants, especially after the first three months. Formula-fed babies tend to gain weight more quickly during the second half of the first year, and these differences persist even after solid foods are introduced. Both patterns are normal. The CDC recommends using the World Health Organization growth charts for all children under two because those charts are based primarily on breastfed infants and reflect how children grow under optimal conditions.
Genetics matter too. Tall parents tend to have longer, leaner babies. Shorter parents often have babies who weigh less. Illness, food allergies, and digestive issues can temporarily slow weight gain, but most babies catch up once the underlying issue is resolved.
When Weight Might Be a Concern
Pediatricians look at patterns, not snapshots. A child who has always tracked along the 10th percentile is generally healthy. A child who drops from the 50th percentile to the 10th over a few months is worth investigating. The clinical threshold for concern is when a child’s weight-for-length falls below the 3rd to 5th percentile, or when they cross two or more major percentile lines on the growth chart.
On the higher end, a chubby one-year-old is rarely a medical concern. Babies need fat for brain development, and most slim down naturally once they start walking and running. Your pediatrician will flag it if weight-for-length is consistently at an extreme.
Growth Slows After the First Birthday
One thing that surprises many parents is how dramatically growth slows in the second year. During infancy, gaining 4 pounds in four months is common. During the entire second year, most toddlers add only 3 to 5 pounds total. Appetite often drops noticeably, and meals become unpredictable. This is normal. A one-year-old who was eating everything in sight may become a picky toddler seemingly overnight, and their growth rate reflects that shift.
How to Weigh Your One-Year-Old at Home
If you want to track weight between pediatric visits, you don’t need a special baby scale. The simplest method is to step on a bathroom scale alone, note your weight, then step on again while holding your child naked. Subtract the first number from the second. For the most accurate reading, place your scale on a hard, flat surface like a kitchen or bathroom floor, not carpet. Digital scales work best.
A few tips for consistency: weigh at roughly the same time of day, ideally before a meal. Make sure your child is undressed, since a diaper and clothes can add half a pound or more. If your toddler squirms, wait for the scale reading to stabilize before recording the number. You can check your scale’s accuracy by weighing something with a known weight, like a 1 kg bag of sugar.
Keep in mind that home scales aren’t as precise as the ones at your pediatrician’s office. They’re useful for spotting trends, but small fluctuations of a few ounces between days don’t mean much. Weekly or biweekly weigh-ins give a clearer picture than daily ones.