Children come in all shapes and sizes. Some are short, some are tall, some are stout and some are thin. Both genetic and environmental factors influence height and weight. The average height and weight of children varies by gender, age, race, ethnicity and nationality. Parents and medical providers monitor a child's height and weight to identify health problems and assure that the child is developing normally.
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Medical providers consult growth charts when they evaluate a child's height and weight. Growth charts display the average weight and height of children according to age and gender. Doctors weigh the child, measure his height, and then find the child's percentile ranking on the growth chart compared to children of the same gender and age. Within a specific age and gender, there is a wide range of body types, heights and weights that are considered normal. A child's height or weight is broadly defined as average or normal if it lies within the fifth to 95th percentile.
Girls’ Average Height
You can review the average height of a toddler-aged child using growth charts, such as those available online at Kids Growth. The average height for a 12-month-old girl is 30.5 inches, and the normal range goes from just over 27 inches to about 31 inches. The average height for a 24-month-old girl is about 34 inches, with a normal range of about 31.5 to 36 inches. At 36 months, girls average about 37.5 inches in height, and have a normal range of just under 35 to 40 inches.
Boys Average Height
The average height for 12-month-old boys is just under 30 inches, with a normal range of just under 28 inches to just under 32 inches. Twenty-four-month-old boys average about 34.5 inches in height, and have a normal range from 32 to 36.7 inches. The average 36-month old boy is about 37.7 inches tall, with a normal range of 34.5 to 40.5 inches.
Girls Average Weight
Just like average height, average weight is estimated using growth charts. The average weight for a 12-month old girl is about 20 lbs., ranging normally from just over 19 to 27.5 lbs. The average weight for a 24-month-old girl is about 26.5 lbs. ranging from 22.5 to 32 lbs. Thirty-six-month-old girls weigh an average of 30.5 lbs., and range from 25.5 to 38 lbs.
Boys Average Weight
The average weight for 12-month-old boys is just less than 23 lbs., with a normal range of 17.5 to 27 lbs. Twenty-four-month-old boys average about 28 lbs., and have a normal range from 23.5 to 33.5 lbs. The average 36-month-old boy is about 31.5 lbs., and ranges from 26.5 to about 38 lbs.
Rate of Change
A child's height or weight at a particular age relative to other children is not the most critical indicator of problems with health or development. Sudden changes in a child's pattern of growth functions as a more important signal of potential problems. Height and weight increase slowly and steadily over time, but doctors become concerned if a child's ranking changes drastically from year to year. For example, a child who moves from the 60th to 40th percentile in height over the course of a year causes greater concern than a child who is consistently at the 10th percentile.
Potential Health Problems
A toddler may have health problems if she displays a significant discrepancy between the percentile ranking for her weight and height. For example, a 3 year old in the 30th percentile for weight but 80th percentile for height may be underweight. A child who has different rates of growth for height and weight may also have health problems. For example, a child with metabolic problems may rise or fall suddenly in height relative to weight over the period of a year.