According to the Centers for Disease Control, the CDC, the average weight for a 12-year-old boy is 90 pounds. At this age, boys in the top 10 percent weigh about 120 pounds or more while those in the lower 10 percent weigh about 70 pounds or less.
The CDC presents information about average height for boys as well. For 12-year-olds, the ranges of height do not differ as much as weight. The average height is about 59 inches, or 4 feet, 11 inches. Boys in the top 10 percent are about 5 feet, 2 inches or taller. Boys in the lower 10 percent of this age group are about 4 feet, 7 inches or shorter.