Every screen I have ever heard of is measured from corner to corner. Televisions, LCDs, Computer Monitors, everything I know of. Always has been. Also, there is a difference is screen size and VIEWABLE screen. For example, if you have a 23" monitor, it may only be 21" viewable. Manufacturers market the total screen size, which is more than the viewable size.
diagonally
Manufacturers measure monitors by screen size. The measurement is taken diagonally, from the bottom left of the screen to the top right corner of the screen.
If you mean a TV's actual size, you measure the screen diagonally
Televisions are generally measured diagonally from corner to corner. The measurement is only the size of the screen and doesn't account for any frame.
The display size of the screen is measured on the diagonal. For instance, lower left hand corner to upper right hand corner. For the TV itself, the size will vary on the case design.
A monitor's size is the distance (usually measured in inches) from corner to corner, diagonally across the screen.This applies to widescreen and normal/full screen monitors.However the manufacturer's specified size might be slightly more than the actual 'viewable size' for a couple of reasons:1. They tend to round-up. So what they might call a 24 inch monitor might actually only be 23.5 inches.2. A CRT monitor's size traditionally includes the casing around the screen, for reasons dating back to the invention of the technology decades ago. This doesn't apply to lcd flat panel monitors.See the related link(s) for a more indepth guide and a tool for getting an approximate measurement of a monitor screen size.By Measuring the monitor diagonally this will give you the screen size.The specific models of the laptops usually have uniform sizes of the screens. So, if you know the model number, you can very easily look up its screen size.
If you mean the screen size, then it is measured by the diagonal of the screen from corner to corner.
Monitors are measured in inches to describe their screen size diagonally. This measurement convention dates back to the early days of television sets, which were also measured in inches. It provides a simple and standardized way for consumers to understand and compare the physical size of different monitors.
Computer monitors are typically measured and marketed by the diagonal length of the screen. The diagonal can be calculated by using the Pythagorean theorem; that is to take square root of the combined height squared plus the width squared.
The same way you measure a TV screen, diagonally (any corner to opposite corner).
You know the size of a monitor by using a ruler to measure the screen diagonally. This applies to both older style CRT monitors and new LCD monitors.
Diagonally across the screen. (From top left to bottom right, or top right to botom left.)