When shopping for new flatscreen LCD monitors, you will find that most screens sold today are widescreen with a 16:9 ratio, meaning that they are nearly twice as wide as they are tall. Older monitors have a 4:3 ratio, meaning that they are nearly square. Since screens are measured diagonally, a new 17″ 16:9 monitor is actually shorter but wider than a 17″ 4:3 monitor. In detail, a new 17″ 16:9 monitor is 8.3″ H x 14.8″ W. An old-style 17″ 4:3 monitor is taller at 10.2″ H x 13.6″ W. Source: cavecreations.com
When shopping for a new monitor, consider the following to find a size that will be equal or greater than your current monitor:
If you have a 17-inch 4:3 monitor, get at least a 22-inch 16:9 widescreen to have the same height. (10.2″ H vs. 10.8″ H)
If you have a 19-inch 4:3 monitor, get at least a 24-inch 16:9 widescreen to have the same height (11.4″ H vs. 11.8″ H)