The average weight of a 13-year-old child is 100.5 pounds. The average height is 61.6 inches, or 5 feet, 1 inch tall. The average waist size for 13-year-olds is 68 centimeters, or 26.7 inches.
Males and females have different weight and height ratios even at such a young age. The average 13-year-old female weighs 101 pounds while her male counterpart weighs in at 100 pounds. At this age, females are slightly taller and heavier than males. While girls are 61.7 centimeters tall, boys reach an average height of 61.5 centimeters. 13-year-old boys typically have an average waist size of 70.5 centimeters, or 27.7 inches, while girls measure in at 65.5 centimeters, or 25.7 inches.