3-Year-Old Boy
On average, a 3-year-old boy weighs about 32 pounds on his third birthday and about 36 pounds at the end of the year, just before his 4th birthday. About 5 percent of boys weigh less than 26.5 pounds on their third birthday and about 5 percent of boys weigh more than 44.5 pounds on their 4th birthday.
3-Year-Old Girl
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The average girl weighs about 31 pounds on her 3rd birthday and grows to 35 pounds by her 4th birthday. However, 5 percent of girls weigh less than 25.5 pounds on their 3rd birthday and 5 percent weigh more than 45 pounds on their 4th birthday.
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Bottom Line
The average 3-year-old boy weighs 33.7 pounds and the average 3-year-old girl weighs 32.7 pounds, both measured at 42 months of age. Most children follow a growth curve established in infancy, and parents should not be concerned unless children deviate significantly from their weight percentile the previous year.