Editing Computer monitor (section)

===Size===
{{Main|Display size}}
[[File:Computer screen dimensions.png|thumb|right|upright=1.2|The area, height and width of displays with identical diagonal measurements vary dependent on [[display aspect ratio|aspect ratio]].]]
On two-dimensional [[display device]]s such as computer monitors the display size or viewable image size is the actual amount of screen space that is available to display a [[picture]], video or working space, without obstruction from the bezel or other aspects of the unit's design. The main measurements for display devices are width, height, total area and the diagonal.

The size of a display is usually given by manufacturers diagonally, i.e. as the distance between two opposite screen corners. This method of measurement is inherited from the method used for the first generation of CRT television when picture tubes with circular faces were in common use. Being circular, it was the external diameter of the glass envelope that described their size. Since these circular tubes were used to display rectangular images, the diagonal measurement of the rectangular image was smaller than the diameter of the tube's face (due to the thickness of the glass). This method continued even when cathode-ray tubes were manufactured as rounded rectangles; it had the advantage of being a single number specifying the size and was not confusing when the aspect ratio was universally 4:3.

With the introduction of flat-panel technology, the diagonal measurement became the actual diagonal of the visible display. This meant that an eighteen-inch LCD had a larger viewable area than an eighteen-inch cathode-ray tube.

Estimation of monitor size by the distance between opposite corners does not take into account the [[display aspect ratio]], so that for example a 16:9 {{convert|21|in|cm|adj=on}} [[widescreen]] display has less area, than a {{convert|21|in|cm|adj=on}} 4:3 screen. The 4:3 screen has dimensions of {{convert|16.8|×|12.6|in|cm|abbr=on}} and an area {{convert|211|sqin|cm2|abbr=on}}, while the widescreen is {{convert|18.3|×|10.3|in|cm|abbr=on}}, {{convert|188|sqin|cm2|abbr=on}}.