A person's weight can be calculated easily by stepping on a scale. However, measuring height from head to toe for some senior citizens and people with spinal problems is difficult to do alone and does not always produce accurate results. Since the arm span of each person is more or less equal to their height, it gives people an alternative method of estimating their height. Calculating arm span and height is easy to do using simple household materials
Read more: http://www.ehow.com/how_8462863_calculate-arm-span-height.html#ixzz2qFL84rsW