For American men 20 years old and up, the average age-adjusted height is 69.1 inches (175.4 cm), or just over 5 feet 9 inches tall....Height by age. Age (years)50th percentile height for boys (inches and centimeters) 1361.4 in. (156 cm) 1464.6 in. (164 cm) 1566.9 in. (170 cm) 1668.3 in. (173.5 cm) Read more...