The average weight for a 9-year-old is approximately 63 pounds, while the average height of a 9-year-old is approximately 52.5 inches. These averages vary slightly based on gender.
On average, children gain 4 to 7 pounds every year until the onset of puberty. Weight is used in conjunction with height to calculate a child's BMI in order to more accurately assess a child's health. A doctor typically tracks height and weight over time using the Centers for Disease Control's clinical growth chart to spot sudden changes and identify potential problems. Normal growth is supported by good nutrition, adequate sleep and regular exercise.