Importance of Maintaining Viewing Distance While Watching TV

Whenever we plan to watch a movie in the theatres, most of us will definitely prefer seats somewhere in the middle, rather than sitting right at the front or way back at the end of the theatre. While it is not exactly the same when it comes to watching TV, we will still search for that prime place which will make watching TV a good experience. What we exactly want to feel is the essence of a horror movie or an action movie, without straining our eyes or suffering a headache.
While this fact is not true that sitting too close and watching TV can cause permanent damage to eyes, it can definitely cause strain which leads to blurry vision. Most people try to squeeze the biggest screen in their homes; however if your room is small, then it is not a smart idea. One must maintain a proper viewing distance while watching TV based on the screen size. In general, it is recommended to maintain a distance almost 1.5 to 2.5 times the diagonal screen measurement away, with about a 30-degree viewing angle. For example, if you have a 40" TV, you should be sitting somewhere between 5 and 8.3 feet away from the screen.
So, why is it important to maintain a proper viewing distance while watching a TV?
The basic reason to maintain a proper viewing distance is to avoid eye strain and headache. Excessive eye strain can cause blurry vision which might cause some minor eye-sight problem in the future. Apart from maintaining a proper viewing distance, you must also watch TV in a proper lighted room. Watching TV in wrong lighting gives rise to unnecessary eye strain as the eyes have to work hard to see the image. Thus, the proper viewing distance should be combined with right lighting to avoid eye fatigue and strain.
Thus, how far should you sit while watching the TV?
Consider watching your TV from a distance of five times the width of the TV screen. So watch a 42" HDTV from 15' away. The 15' feet distance was a bit far. However, if you feel that too far, maintain a 10-12' distance on the 42" HDTV. Again, if you are watching a 52" TV, maintain a distance of 6.5' - 10.8' (2.0 m - 3.3 m) from the screen.
Hence, as a piece of advice use your sense and move away from the TV if your eyes start hurting. Make sure to watch TV from a distance that will enable you to read texts comfortably on screen without glaring or straining your eyes.

someone told me that you get eye strain from watching tv too long . (Btw, this is copy/past) You're a leech

Personal taste, the location in the room, the resolution of the TV pictures you are watching and even the quality of your eyesight can affect your opinion of the right size of TV for your room.

You can put two different people in the same room, with the same size TV, and both may well have a different opinion of the right size screen for that room and the best viewing distance.

However, it can help to get some solid numbers to give us a starting point, so let us consider how we might do this. There are two ways to approach the issue:

Decide on your screen size and calculate the ideal viewing distance
Estimate your viewing distance and calculate an ideal screen size
A good rule of thumb is that the ideal viewing distance for a flat screen HDTV is between 1.5 and 3 times the diagonal size of the screen - and we can use this to calculate both approaches.