How to Measure a Television Screen

How to Measure a Television Screen
Image Credit: Photographer, Basak Gurbuz Derman/Moment/GettyImages

When you're shopping for a new television, especially a big, flat screen model, it's important to understand how television screens are measured. TV sizes are typically described by a single number, such as 40 inch, which refers to the diagonal measurement of the screen from the lower left corner to the right upper corner. Most manufacturers also provide the exact width and height as part of the television specifications. It should be noted that the diagonal measurement is for the television screen and not the enclosing frame.

Measuring a TV Screen

The best way to measure a TV is with a soft tape measure. If you use a metal tape measure or ruler, be careful not to come in contact with the screen while measuring since you could scratch it. Hold one end of the tape in the lower left corner of the screen and stretch the tape to the upper right corner. For a very large screen, you may need someone else to hold one end of the tape.

Besides the diagonal measurement, it's also important to measure the width and height of the screen if you're shopping for a TV stand or planning on a wall mount. If you don't have a tape measure and know the make and model of the television, check online for the exact screen dimensions. When shopping for a TV stand, look for a solid piece of furniture that's at least a few inches wider than the set. Using a smaller stand is dangerous since the TV can tip over. Use the full width measurement of the television frame, or bezel, rather than just the screen to determine the best size for a TV stand.

Screen Size vs. Resolution

The physical dimensions of a television screen are not the same as the screen resolution, which refers to the number of pixels that make up the display. Each pixel is one dot of color on the screen. When you hear about a 4K resolution, it usually means the screen has 3,840 × 2,160 pixels. This resolution is also known as ultra high definition, or UHD. Most televisions that have a diagonal measurement of 50 inches or higher are UHD.

Screen that are 40 inches or smaller typically have a resolution of 1280 × 720 pixels, also known as 720p resolution. Another popular resolution is 1920 × 1080 pixels, or 1080p. This resolution is also referred to as full HD. The picture quality of full HD is not generally not as clear and sharp as ultra HD.

TV Viewing Distance Formula

Besides considering the size of your space when looking for a television, you should also take the viewing distance into account. Large screen televisions need larger rooms for optimal viewing. Experts say the ideal distance for viewing a non-HD television is twice the screen size, so screen size × 2 = viewing distance. Sitting closer than this calculated distance poses the risk of eyestrain.

For a 48-inch TV, the viewing distance should be 2 × 48 = 96 inches, which is 8 feet. You can use the inverse formula if you know the viewing distance and want to calculate the best TV size for the space. For example, if the viewing distance is 5 feet, or 60 inches, then the ideal television is 60 ÷ 2 = 30 inches. Remember, this is the diagonal measurement of the screen.

According to television manufacturer Sony, televisions with 4K screens can be watched from a closer distance because they of 1.5 times the screen's vertical height. From this distance, the human eye cannot discern individual pixels. So for a 50-inch screen with a vertical height of 27 inches, the viewing distance can be 27 × 1.5, which is about 40 inches or 3.3 feet.