How many bones does an adult human skeleton normally have?

An adult skeleton settles at 206 bones, but you did not start with that number. A newborn has roughly 270 separate bony and cartilaginous pieces, and over childhood and adolescence many of them fuse. The skull begins as separate plates joined by flexible sutures so the head can compress during birth and then expand as the brain grows. The sacrum at the base of the spine starts as five separate vertebrae and knits into one triangular bone, and the tailbone fuses from several more. The long bones of the arms and legs have growth plates near their ends that keep producing new bone until they close in the late teens or early twenties, at which point height stops increasing. Of the 206, more than half are in the hands and feet, which need many small bones to be both strong and flexible. The count varies slightly between individuals, since some people have extra ribs or small accessory bones in the feet.

The smallest bone in the body is the stapes in the middle ear, only a few millimetres long.