 For example, a 168cm (5ft 6in) person will have an arm span of about 168cm (66in).Age, sex, and ethnicity have to be taken into account to best predict height from arm span.Arm span is sometimes used when a height measurement is needed but the individual cannot stand on a traditional stadiometer or against a wall due to abnormalities of the back or legs, such as scoliosis, osteoporosis, amputations, or those who are confined to a bed or wheelchair.