The typical weight for 13 year old girls ranges from 82 to 137 pounds, the average weight being around 102 pounds. The average weight for 13 year old boys is around 102 pounds, which can range from 80 to 135 pounds. For girls aged 13, the typical height ranges from 4’11¼”to 5’5¾“, the average height being around 5’1¾“. For boys aged13, height ranges from 4’11” to 5’5¾“, the average height being 5’1¾“.