As young parents 38 years ago, we were told that if you measure the height of your child exactly on their second birthday, their adult height will be exactly double that. This appealed to me (Bob) since I am a scientist and the experiment is easy and safe to perform. The people we heard this from swore by it. Sooooo....we measured Michelle and Melissa on their second birthdays at exactly 35 and 36 inches and kept track of the numbers on the back of our basement measuring door. Years later in their early 20's their heigths were 70 and 72 inches or exactly double what they were on their second birthdays. When we used your calculator, the predicted height for these two young women was only 68 inches which was wrong by 2 and 4 inches. It would be interesting to have more people share their experiences about this method and their results or thoughts. Bob and Mary