The average length of a human arm is 25 inches. However, the length fluctuates because the average length for a young guy of average height and health is 25 inches.
The average arm length is as variable as the average height. It is generally acknowledged that there is a correlation between the two; if a person is taller, they will likely have longer arms than those who are shorter. In contrast to adults of the same height, children tend to develop proportionally longer arms as they grow. The arms of a 5-foot-tall child are likely slightly longer than those of a 5-foot-tall adult, presuming the youngster has not yet reached his or her maximum height.