Is it possible to determine how big a junior athlete of 13 years old will be at 18 years old. We have begun working with some exceptional junior athletes and this question has come up. Can this be determined from any type of Measurement?
According to Pediatric Rheumatologist Melissa Hawkins-Holt, MD (my wife), there is no reliable measurement to indicate how big a 13-year-old will be at 18.
Obviously the height of the parents, grandparents, and older siblings gives some indication, but is clearly not conclusive.
Another common and equally unreliable estimate is to compare percentiles from the CDC growth charts. This assumes that the athlete remains in the same percentile as he ages (which is clearly not always the case). You can find those charts at http://www.cdc.gov/nchs/about/major/nhanes/growthcharts/clinical_charts.htm
Unfortunately, the short (pardon the pun) answer to your question is, "No." Of course Mugsey Bogues and Spud Webb and even 6' Allen Iverson will be glad to tell you that height doesn't matter.