How to measure a TV screen in inches

Updated February 21, 2017

The size of a TV screen can be quite confusing sometimes, especially as we undergo the transfer from older analogue TVs to newer flat screen TVs. The measurements are uniform for all types of TV, but those measurements can sometimes be deceptive. This can wreak havoc if you require a set amount of space for your TV or are measuring it to fit into an entertainment centre. You can measure the TV screen in inches using a few quick formulas that will help cut through the confusion.

Measure the size of the area you wish to use for your TV. Gauge the height, the width and the depth. That sets your parameters. If you are replacing an old TV with a newer one, measure both the size of your existing TV screen (height, width and diagonal length) and the overall size of the TV (height, width and depth).

Know that TV manufacturers list the size of the TV by diagonal inches. This is the number that they use on the advertising. It works fine if the TV screen is of a comparable shape, but less so if there is a variation. Older TVs use a 4:3 aspect ratio for their screens, while newer TVs have a 16:9 aspect ratio for theirs. To put it more bluntly, you could buy a flat screen TV of the same listed size (diagonal length) as your old TV and actually end up with less screen space.

Compare the height of the old TV to the height of the new one. If they match, then the new TV will either have the same size screen or a slightly bigger screen. If you're buying a wide screen TV to replace an older TV, you can perform a quick piece of arithmetic to determine the right size without using a tape measure. Multiply the diagonal length of your older TV by 1.22. The result is the number of list (diagonal) inches the widescreen TV needs to be in order to match the size of your existing TV.

Purchase a TV that fits your measured space. That includes the full height, width and depth, not just the height, width and depth of the screen. With newer flat screen TVs, the difference will be minimal (not more than a few inches) because the advance in technology allows the screens to take up a greater percentage of the TV's surface.


When using a tape measure, work carefully to avoid scratching or marring the surface of your TV.

Things You'll Need

  • Tape measure
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