During the first year of life, an infant may double or triple his birth weight, according to the American Academy of Pediatrics. During childhood, this dramatic growth slows to a steadier pace. Weight gains are calculated according to a child's height and age. A child's weight is plotted on a chart, and weights above the 5th percentile and below the 85th percentile are considered normal weight, according to Kids Health.
Ages Two to Three Years
The average toddler measures 31.5 to 42.5 inches between the second and third birthday, according to Boston Children's Hospital. Weight may span from about 22 to 34 pounds at age two, and from 26 to 38 pounds at age three. Your toddler's pediatrician will document her length and weight on a growth chart. Some children may be taller and heavier than these averages, and being outside of the percentiles on a growth chart does not mean that a child is necessarily over- or underweight, according to Kids Health.
Ages Four to Eight Years
A child may grow more than 10 inches between his fourth and eighth birthdays, and may also gain as many as 30 to 40 pounds. A four-year-old standing about 40 inches typically weighs between 28 and 44 pounds, according to Boston Children's Hospital. Six-year-old children measure 42 to 49 inches tall and may weigh between 36 and 60 pounds. By the eighth birthday, your son or daughter may range from 4 to 4 1/2 feet tall and may weigh from 44 to 80 pounds.
Ages Nine to Twelve Years
Your child's growth spurts grow more pronounced as she approaches puberty. Children during this phase of life may gain up to about a foot in height and as many as 50 pounds in weight. A 10-year-old may average 4 to 5 feet in height, and weight may range from 54 to 106 pounds. A child at 12 years old may range from 4 1/2 feet to about 5 1/2 feet tall, and may weigh from about 65 to 135 pounds, according to Boston Children's Hospital.
Ages Twelve to Sixteen Years
Children typically reach their adult height and weight during the mid-teenage years, though some children may grow throughout their teens and into their early twenties. Heights span from about 5 feet to about 5-foot-10 at age 14, with weights ranging from about 85 to 160 pounds. When children reach 16, heights vary from about 5 feet to about 6 feet. Children this age should be close to an adult weight, ranging from 95 to 185 pounds, according to Boston Children's Hospital. This is also the age range when girls' sizes begin to vary more from boys'. At younger ages, girls and boys tend to have very similar ranges of height and weight. For example, at age four, girls are 37 to 42.5 inches and 28 to 44 pounds, while boys are 37.5 to 43 inches and 30 to 44 pounds. However, by age sixteen, girls' typical heights are 60 to 68 inches, while boys are 63 to 73 inches, and girls tend to weigh about 94 to 172 pounds, while boys generally range from 104 to 186 pounds, in keeping with their greater height.