Measure the distance between the lying opposite each other angles of the monitor screen is the diagonal. You need to measure the distance of the diagonal of the housing, namely between the corners of the screen, i.e. the visible surface of the matrix liquid crystal display (LCD) monitor or a CRT monitor using a cathode ray tube (CRT). Search for this operation, the measuring tool with the applied tick marks, in inches, is not necessary, since the result can easily convert from centimeters to inches.
Share measured in inches the diagonal of the monitor by a factor of 2.54 to convert it into inches - it is the ratio since 1958 established in the UK and the USA using non-metric system of measures.
Manual measurement you will get real visible diagonal screen but if you need to know the certified value of this parameter, keep in mind that it may not coincide with the measured ones. The difference could be due to the fact that some part of the screen obscured by the case in which you installed the matrix or tube. Learn certified value in factory description of set of accompanying documents that you purchased the monitor from marks on its body or from the full name of the model. For example, in the name of Philips 220WS the first two digits (22) indicate the diagonal size in inches. To see the full name on the body of the device or on the packaging box and the display properties in your operating system.
If you know the size of the tube or matrix of the monitor, if necessary, convert it to centimeters, multiply this number by a factor of 2.54. But we can not deal with calculations and use built-in search system Google unit Converter. For example, for translation in centimeters of the diagonal of the monitor Philips 220WS enter a search term "22 inch in centimeters".