A person's arm span is not equal to their height. Arm spans are longer than height by approximately 2 inches in adult males and approximately .5 inch in adult females.
Boys up to 10 years old and girls up to 11 years old are typically shorter than their arm spans. Abnormal arm span to height ratios may be indications of medical disorders, such as Marfan's syndrome and homocystinuria. Abnormal arm span lengths, however, are normal in patients with spine deformities, such as spondyloepiphyseal dysplasia. Such conditions make it difficult to stand up properly, thereby resulting in abnormally long arm spans.