We recommend buyers spend time thinking about three things when deciding what size HDTV to buy:
1. The physical dimensions of the living room.
2. What type of programming you will be watching on your TV.
3. Most importantly, the distance you will be sitting from the television.
The Viewing Room
Decide where in the room you want to place the television; measure the overall dimensions of your viewing room and the available area around where you will be placing the TV while allowing room for additional components and speakers. This will give you a better idea of how everything will look once you get your new TV home.
Make sure you consider the overall physical dimensions of any TV in order to ensure that it's not too big for the room - and don't forget to include the components.
What type of programming will you be viewing on your new TV? Determine how much of your viewing will be spent watching low quality Standard Definition (SD) programming, mid-quality DVD programming and high quality (HD) programming.
The important factor here is the bigger the TV, the more likely you'll see imperfections of low-quality programming. Since an HD signal is superior to other signals, you can buy a bigger screen without being distracted by imperfections.
Optimal Viewing Distance
There is a formula for determining the sweet-spot viewing distance for a particular sized HDTV. For instance, if you plan to buy a 50" HDTV, you would multiply the diagonal screen inches by 1.65 (50" x 1.65 = 82.5"). This resulting number is the distance at which the HDTV will look its absolute best. So, in this case, it would be 82.5" or just under 7 feet for a 50" HDTV. This doesn't mean a 50" HDTV won't still look good from a longer distance such as 9 or 10 feet but we would recommend considering a larger HDTV in those cases.
Optimal Viewing Dist in Feet = (Screen Size in Inches x 1.65) / 12
Remember that a widescreen HDTV has less viewing area than an old standard definition TV. This is because the screen is wider (16 x 9 ratio) and less tall so a 50" HDTV may not look as big as your old 50" SDTV (4 x 3 ratio). Also, when figuring the optimal viewing distance, you should typically not sit much closer than that or you may start seeing what is called the "screen door" effect. This effect means your eyes may be able to discern each individual pixel so that it almost appears as if you're viewing through a screen door.
How HDTV Size is Measured
A TV is measured diagonally based on its screen size, so a 32" television means that the screen is 32" when measured from the bottom left corner to the top right corner.