How to measure a TV screen diagonally

Written by david thompson
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How to measure a TV screen diagonally
Manufacturers have categorised TVs by diagonal measurements for decades. (old television image by inacio pires from

Manufacturers list TV screen sizes by diagonal measurement. Televisions come in two different aspect ratios, though, so two TVs with the same diagonal measurement may have different heights and widths. Measure your screen diagonally, then if you want to find the aspect ratio, input the diagonal measurement into an online aspect-ratio calculator to find out what the height and width should be for a 16:9 or 4:3 aspect ratio (See Resources). Measure the height and width of your screen to see which it matches.

Skill level:

Things you need

  • Tape measure

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  1. 1

    Hold one end of a tape measure at the lower left corner of the TV screen, where the screen itself meets the frame.

  2. 2

    Extend the tape measure to the upper right corner of the screen, where the screen meets the frame.

  3. 3

    Round the exact measurement to the nearest inch.

Tips and warnings

  • Some CRT monitors may have a picture area slightly smaller than the actual diagonal measurement. To see what the exact size of the picture itself will be, turn on the monitor and notice whether there's a narrow border between the picture and the edge of the screen.

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