Approximately 17 percent of children qualify as obese, according to the Centers for Disease Control and Prevention. Obesity puts your child at an increased risk for health problems such as type 2 diabetes and heart disease. At times, it can be hard for parents to tell just by looking at their school-age child whether he is at a normal height and weight, especially since both weight and height can vary fairly significantly, depending on how quickly the child is developing.
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5- to 6-Year-Old Children
The range of "normal" for height and weight is quite broad in school-age children; it's defined as between the 5th and 95th percentile on the age and weight charts. At the age of 5, a typical child is about 43 inches tall and weighs about 43 pounds; however, even children in the same year of school can vary by as much as 5 inches in height. A normal height is around 39 to 48 inches for a 5-year-old boy or girl, and a normal weight is between 34 and 63 pounds.
Children grow about 2 inches per year, with perhaps a bit more of a growth spurt occurring between the ages of 6 and 8, and they usually gain about 6.5 pounds each year during middle childhood. By 6 years of age, the normal height range for a child is 42 to 51 inches, regardless of gender. The healthy weight range is 36 to 68 pounds.
Even if your child falls within the normal ranges for both weight and height, she may be too heavy or too light for her height. Determining body mass index gives you a better idea of whether or not your child is at a healthy weight for her height. Any percentage between the 5th and 85th percentile on the body mass index-for-age charts is considered healthy, while above this percentage is considered overweight; below is underweight. The normal BMI range for a 5- or 6-year-old boy or girl is from 14 to 17.
7- to 9-Year-Old Children
When they're 7 years old, boys and girls are of similar heights, ranging from 45 to 54 inches, and by the time they reach the age of 9, their average height is 48 and 59 inches.
Like younger children, girls in this age group have a wider weight span than boys. At 7, a boy should weigh between 41 to 82 pounds, and a girl should weigh between 40 to 84 pounds. By 9, typical weights for boys are between 50 and 108 pounds; for girls, it's from 49 to 112 pounds.
A 7-year-old girl may have a slightly lower BMI than a boy of the same age, however, and still be within the healthy range, which is 13 to 18 for girls and 14 to 18 for boys. By the time children turn 9, the recommended range for BMI is the same -- 14 to 20.
10- to 12-Year-Old Children
While boys and girls are approximately the same height at age 10 -- from 50 to 61 inches tall -- by the age of 12, they vary slightly, with a normal height range for a boy between 54 and 67 inches. For a girl, it's between 55 and 66 inches.
As many children are beginning to enter or in the midst of going through puberty at this age, girls tend to be a bit heavier than boys. For example, while a 10-year-old boy should weigh from 55 to 123 pounds, a girl of the same age is expected to weigh from 55 to 128 pounds. Although the average 12 year old is about 59 inches tall and weighs about 90 pounds, the same weight difference exists at 12 years old, with a normal weight for boys of 67 to 154 pounds; for girls, it ranges from 69 to 158 pounds.
The recommended range for BMI allows for these heavier weights in girls, extending slightly past that of boys. A 10-year-old boy should have a BMI between 14 and 20, but a girl of the same age is expected to have a BMI of 14 to 21. These recommended BMI spans increase slightly for 12 year olds, with boys ranging from 15 to 22; for girls, it ranges from 15 to 23.
Puberty typically begins between the ages of 8 and 14, and even when they begin, some kids develop more quickly than others. Girls can start puberty as young as 7 years old, however, and boys may begin puberty as early as 9 years old.
During puberty, your child's muscles, bones and fat will grow, leading to greater increases in weight and height. Girls typically develop a higher percentage of body fat, while boys tend to gain more muscle. Boys and girls will be about the same height until puberty; girls then temporarily becoming taller than boys, since they usually begin puberty at an earlier age. After boys hit puberty, they usually catch up with girls in height and often pass them.
The changes that occur during puberty make it harder to determine what is normal, which is why you won't find a set height or weight for each age. Instead, expect a range of the typical weights and heights.