Screen size calculator
A 65-inch television is not 18% larger than a 55-inch one — it is 40% larger by area, because area grows with the square of the diagonal. That is why the step from 55 to 65 feels so much bigger in a room than the numbers suggest, and why comparing screens by diagonal alone consistently understates the difference.
A 55-inch 16:9 screen is 47.94 inches wide and 26.97 high — 121.8 by 68.5 centimetres. Area grows with the square of the diagonal, so a 65-inch screen has 40% more area than a 55-inch one, not 18%.
How to find real screen dimensions
The advertised diagonal is the panel, not the product. A television or monitor is wider and taller than these figures by the bezel, and a stand adds depth and height that the specification often buries. When measuring for an alcove or a wall mount, the panel dimensions here are the floor and the manufacturer product dimensions are what actually has to fit. Ultrawide monitors are the case where the difference is most striking — a 34-inch 21:9 is barely taller than a 27-inch 16:9 but nearly 20 cm wider.
Questions
About 47.9 inches or 121.8 cm of panel, plus the bezel.