How to Measure the Inches on a Computer Monitor

By James Johnson

When choosing which computer monitor to buy, it becomes quickly apparent that there is more to a computer's display size than a single dimension. For example, some monitors simply state a size, such as 17 inches, while other monitors state "17 inches diagonally." In most cases, a monitor's size is measured diagonally and it is important that buyers know how to determine that size.

Things You'll Need

  • String
  • Marker
  • Measuring tape

Step 1

Place a piece of string from the bottom left screen corner and run it across your screen to the top right corner. You can also run a string from the bottom right corner to the top left, if you prefer. Mark the string with a marker/pen or simply hold the pieces at each end.

Step 2

Place the string down on a flat surface and measure the distance you have marked off. This will give you the distance between the two corners, which is considered the monitor's diagonal size. This is the standard size used by most monitor manufacturers.

Step 3

Measure the distance between the corners using the inches scale on your tape measure. If you do not have the size in inches, you can also and change centimeters and other measurements into inches (see Resources).

Step 4

Measure the monitor's corners with a tape measure, if you choose. Keep in mind that the metal ends of a typical tape measure may scratch your computer's monitor or trim. Another alternative is to use a tailor's tape measure that doesn't have metal contact areas.

Tips & Warnings

  • Check with the monitor's manufacturer to determine the "viewable size" of the monitor. In some cases, an "18-inch monitor" may be measured from the outside corners, while the viewable space may be closer to 15 or 16 inches.