This article is about the physical measurement. For other uses, see Reach.
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Arm span or reach (sometimes referred to as wingspan, or spelled "armspan") is the physical measurement of the length from one end of an individual's arms (measured at the fingertips) to the other when raised parallel to the ground at shoulder height at a 90° angle. The arm span measurement is usually very close to the person's height. 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. Other, possibly more accurate measuring techniques include knee length or recumbent length when possible.
Because any decrease in height will cause an increase in the ratio of arm span to height, a large span to height ratio may sometimes be an indicator of a health problem that has caused a decrease in height.
An above-average reach is advantageous in sports such as basketball, tennis, boxing, volleyball, discus throw, fencing, rock climbing, and swimming. For instance, the boxer Sonny Liston had a 213cm (7ft) reach despite being 185cm (6ft 1in) in height. This unusually long reach allowed him to hit opposing boxers from relatively safe distances where they could not reach him. However, a long arm span is mechanically disadvantageous on the bench press.
The most common and easily accessible method of measuring armspan uses the demi-span. Using a tape measure, measure from the individual's sternal notch (center of the breastbone) to their middle finger as it is stretched out to one side, then either plug the result into a formula to estimate height, or double the demi-span for the actual armspan measurement. Demi-span is used because measuring from fingertip to fingertip is difficult, requiring two people or markings on a wall.