In a method of operating a measurement device, an image acquisition unit acquires a first image of a subject. A display control unit displays the first image or a second image regarding the first image on a display. A reading unit reads one or more pieces of reference information from a storage medium. The reference information represents two reference positions on the subject. The display control unit displays the one or more pieces of reference information on the display. A setting unit sets two reference positions on the first image or the second image after the first image or the second image is displayed on the display and the reference information is displayed on the display.