The average weight of a 13-year-old boy typically ranges between 34 kg and 63 kg (75 to 138 pounds). More precisely, the average or 50th percentile weight is about 45 kg (100 pounds), with healthy weights ranging from approximately 34 kg (75 pounds) at the lower 5th percentile to about 63 kg (138 pounds) at the 95th percentile. This variation depends on factors like height, puberty stage, and individual development.