 Hair length is most often measured ( in centimeters or inches ) from the line of the scalp on the forehead up over the highest point of the skull to its termination , and sometimes from the crown , the latter resulting in 10 centimeter lower values in average . In cosmetology , hair lengths are usually categorized according to the part of the body where the bulk of the longest hair terminates : chin level , shoulder length , lower shoulderblade / mid @-@ back level , waist length , hip @-@ length , classic length ( extends to almost buttock @-@ length , i.e. upper thigh @-@ length , where the legs meet the buttocks ) , thigh @-@ length , knee @-@ length and ankle / floor length hair . 
