That depends on the size of the television. Crutchfield has an article on it here.

its perspective. i am contemplating rigging up a flexible arm mount so i can place my 27-32" tv about 3-4' away. why have a 65" tv that is 13' from your face?

So there is a CEDIA article on it for 1080p resolution that says that in general seating distance should be 3x times the vertical dimension of whatever display you are using. So if you have a 75" 1080p display that has a vertical dimension of 38" then 3 times that would be 114" or roughly 9.5ft. Now with 4k displays ideally that distance should be shortened a bit as when you compare the equivalent size 1080p to 4k display the 4k display has the optical illusion of feeling "smaller." Given this it is really user preference as there is no end all be all standard that will fit everyone.

It depends on your TV resolution. 1080p is usually 2-3X the distance of your screen size. 4K it is much closer; half of that of the 1080p or even closer viewing. That why people are choosing bigger 4K models - closer greater the detail of the picture quality; it after all 4X more detail!

Depends in part on how immersed you like to be in the tv experience. I've been visiting friends whose sitting room tv is approx 36 inches, and we've watched from 10 feet away, for me it's been fine.