What's the right screen size for a particular viewing distance? What's the best distance to watch a certain sized tv? Since standard definition televisions always have a screen ratio of 3:4, and high definition (wide screen) tv's are always 9:16, you only fill in one field for the column and the rest will be computed. The number that you enter will appear in red. The calculated numbers will be black. Screen size calculations need to be adjusted to a size that is actually available from a manufacturer. If you use inches for your input value, the other measurements will also be in inches. The same is true for feet, centimeters, etc.

Note: The high def values are ideal because they don't take into consideration watching a standard definition show on the same set. The compromise values adjust the screen size or the viewing distance to improve the picture when a high def set shows a standard def picture.