Optimum HDTV viewing distance could protect your vision. the TV viewing distance could help you find the best viewing distance according to your TV screen Size. If your living room distance has been identified, you could find the suitable TV size.
Where DS is Display's diagonal size, VD is Viewing distance, NVR is Display's native vertical resolution (in pixels), NHR is Display's native horizontal resolution (in pixels), CVR is Vertical resolution of the video being displayed (in pixels)