If I still remember it right, my father used to remind us before — during our childhood years, in watching TV the proper and recommended TV viewing distance for kids. He did not measure physically in front of us but he put a mark on our floor for us not to stay beyond it while watching TV.
Image source slowburn.typepad.com
I didn’t mind those things and dig more about them not until I grew up and learned to get curious on every single thing my parents told us and fairly understood from them as well.
Having experienced those and learned from my parents, I and my siblings also taught the kids at home the recommended TV viewing distance for kids. Since we do not have TV wall mounts at home, and the television set was just placed in a shelf, the kids were taught not to go near to it. And as what my parents said, the nearer you gets to the TV, the more damage it causes to the eyes even if it has screen protector on it. That was what we also told to the kids; obedient enough, they also followed.
I personally do not know how to compute the recommended TV viewing distance for kids and adult. But upon doing some personal research about it, I stumbled upon us.toshiba.com recommended TV viewing distance article which I found very useful. According to them, just simply multiply the TV screen size by 1.2 (min distance) and 1.9 (max distance) and then divide the result by 12 to get the right number of feet. For instance, the best distance for a 55” set would be approximately 5.45, or about 5.5 feet.