The height a person reaches as an adult depends on the genes they inherit from their parents as well as general health and nutrition during their years of growth.The fastest period of growth is before birth, with the baby growing from almost zero to a length of about 50cm in nine months. This speed falls after birth with an average growth of 5.5cm per year at eight years old. During puberty, growth speeds up again. This is called the pubertal growth spurt. Before puberty, boys and girls grow at similar speeds, but during puberty boys grow more than girls. The average height of an adult man is 14cm taller than the average height of an adult woman.
Bones increase in length because of growth plates in the bones called epiphyses. As puberty progresses, the growth plates mature, and at the end of puberty they fuse and stop growing. The whole of the skeleton does not stop growing at the same time; hands and feet stop first, then arms and legs, with the last area of growth being the spine. Growth slows down and stops when a child has gone all the way through puberty and has reached an adult stage of development. This means that growth does not stop at a particular age, but children who are ‘early developers’ will stop growing before late developers. After the growth plates fuse, there is no more increase in height, and we all then shrink gradually as we get older. Here is more on this.