Two standards, two answers, and what this page follows
The recommendations people quote come from two different bodies with two different purposes. SMPTE, the engineering society behind broadcast and cinema standards, has long recommended that a screen fill roughly 30 degrees of the viewer's horizontal field of view. THX, which certifies cinema and home theatre installations, recommends closer to 40 degrees, with 36 as a frequently cited minimum. Neither is wrong. SMPTE's figure comes out of a reference viewing environment for evaluating picture quality; THX's comes out of reproducing the experience of a good cinema seat.
The numbers on this page are computed from that geometry directly: the screen's actual width, halved, divided by the tangent of half the chosen angle. That gives the distance at which the screen subtends exactly 30 or exactly 40 degrees. The range you get is the span between the two, and the honest summary is that any distance inside it is defensible. Where the two agree is that most people sit too far away, which is a consequence of buying a television sized for the wall rather than for the seat.
The resolution limit, and why it moves the near end
Separately from comfort, there is a hard optical limit on how close you can sit before you can see the pixels. Normal 20/20 vision resolves about one arcminute of detail, which works out to roughly 60 pixels per degree of view. A 1080p image is 1920 pixels across, so it can cover about 32 degrees before the structure becomes visible. A 4K image covers 64 degrees, and 8K covers 128 — far more than any comfortable seat.
This is why resolution changes the answer at the near end only. At 1080p the pixel limit lands close to the SMPTE figure, so the recommended window is narrow and starts fairly far back. At 4K the limit is well inside anything comfortable, so the near end is governed by immersion rather than by pixels, and you can sit at the THX distance without seeing structure. That is the real practical benefit of 4K in a living room: not that it looks sharper from where you already sit, but that it lets you use a bigger screen at the same seat.
Measuring the distance correctly
The measurement is from your eye to the screen, along the straight line between them. Two errors are common. The first is measuring from the front of the sofa; people sit back into cushions, which puts their head a foot to eighteen inches farther away than the furniture's front edge suggests. The second is measuring along the floor when the screen is mounted high, though this only matters when the height difference is large.
Screen height matters too and is not part of the distance calculation at all. Comfortable viewing puts the centre of the picture at or slightly below seated eye level. Televisions mounted above fireplaces are almost always too high, and no viewing distance fixes the neck extension that causes.
Desk monitors are a different problem
None of the above transfers cleanly to a monitor, and it is worth saying plainly that there is no equivalent standard for one. Film viewing is about filling your vision; desk work is about reading text for hours without eye strain or neck pain, and the constraint is legibility and posture rather than immersion. The usable guidance is arm's length as a starting distance — typically 20 to 30 inches — with the top of the screen at or just below eye level, and text sized so that you are not leaning in. If you have to lean, increase the text size instead of moving the screen. A very large monitor at a desk fails not because of any viewing-angle rule but because the corners fall outside the region your eyes cover without head movement.
What this cannot account for
Content quality outranks all of it. A well-mastered 4K film supports a close seat; a heavily compressed stream shows its artefacts at exactly the same distance that makes the good material look best. Your own eyesight is a variable the standards assume away — the 60 pixels per degree figure describes 20/20 vision, and a great many people watching televisions do not have it, corrected or otherwise. Room lighting, how long you are watching, and whether you are reading subtitles all move the comfortable distance around. Take the range as a bracket to start from, sit in it, and move the chair.
Questions people ask
How far should I sit from a 65 inch TV?
A 65 inch 16:9 screen is 56.6 inches wide, which puts the 40 degree THX distance at about 6 feet 6 inches and the 30 degree SMPTE distance at about 8 feet 10. At 4K the pixel limit is around 3 feet 8, so it does not constrain anything, and the whole range is available. At 1080p the pixel limit moves out to about 8 feet 3, which collapses the window to almost nothing and is a fair summary of why 1080p sets stopped being made at this size. Most living rooms put the sofa between 8 and 11 feet out, which is at or beyond the relaxed end — the common situation is a television slightly too small for the room rather than too large.
Which standard should I follow, THX or SMPTE?
Follow the one that matches what you watch. THX at 40 degrees is aimed at film with the lights down and reproduces a good cinema seat; it is more involving and more tiring, and it demands well-mastered content because the screen occupies enough of your vision that flaws are unavoidable. SMPTE at 30 degrees is more relaxed, better for daytime television, sport, gaming sessions where you need to see the whole screen at once, and rooms where people are half-watching. If you cannot choose, the middle of the range is a reasonable default, and it is worth noting that neither organisation intended these as consumer purchasing advice in the first place.
Does 4K mean I can sit closer?
Yes, and that is essentially the whole of what it buys you at normal living-room distances. Resolution sets how close you can get before pixels are resolvable, and 4K roughly halves that distance compared with 1080p at the same screen size. It does not make the image look sharper from a seat where 1080p pixels were already invisible — from 10 feet on a 55 inch set, most people cannot distinguish the two on real content. The practical reading is that 4K lets you put a larger screen at the same distance, not that the same screen looks better.
Is there a minimum distance for a computer monitor?
Not one anybody has standardised, but around 20 inches is a sensible floor and arm's length is the usual working advice. Closer than that and the eyes converge and accommodate hard for the whole session, which is where the ache comes from. The other half of the answer is text size: people move monitors closer because the type is too small, which trades an eye problem for a neck problem. Increase the scaling first, put the top of the screen at or slightly below eye level, and set the distance by where your arm falls comfortably.