Most common TVs have screen sizes between 32 and 84 inches. Screen size refers to the diagonal measurement from opposite corners. Modern flat screen high-definition televisions are much larger than earlier cathode ray tube televisions, which typically had screen sizes of less than 36 inches.
The size of a television's screen usually refers to its diagonal measurement. However, all televisions display images as a large number of individual pixels, small squares or dots of colored light. For this reason, the number of pixels a television uses is another way of measuring its display size. The actual measurement of a television screen is formally called its physical image size, while the number of pixels the screen uses to display an image is called its resolution.
Display resolution describes how many horizontal lines of pixels the television has on screen at once. For example, a standard high-definition television displays 720 horizontal lines of pixels at once, while a full-HD television displays 1,080 horizontal lines. These designations give standard high-definition and full-HD the abbreviations 720p and 1080p, respectively.
The size of the room in which the owner places the television has a large impact on the quality of the visible image. If an owner places a massive 84-inch 1080p display in a tiny room, for example, the picture quality suffers as viewers can discern individual pixels in the image.