The average 3-year-old boy is 35.75 to 40.25 inches tall. Average weight for this age is 26.5 to 38.5 pounds. The average 3-year-old grows 2 to 3 inches per year and gains about 4 to 6 pounds per year.
A child's growth at the age of 3 is much slower than his first year. By the time the child is 3, he should begin to run and jump easily, walk up and down the stairs without assistance and feed himself well with a spoon. A 3-year-old also has all baby teeth and vision that is very close to 20/20. Speech development also improves significantly at this age.