TV Size Calculator

How to choose the right TV size for your room

The best TV size is not a fixed number — it depends on how far away you sit. A screen that looks huge across a small den can look small from the back of a large living room. Rather than guess, size the TV by the viewing angle it fills: the share of your field of view the picture takes up. That is exactly how home-cinema standards define a good screen.

This TV size calculator turns your viewing distance into a recommended screen diagonal. It works from the image width that hits a target viewing angle, then converts that width to a 16:9 diagonal, which is how TVs are sold.

Mixed use vs cinema: the two standards

• Mixed use (30°): SMPTE's recommended minimum viewing angle. A balanced pick for a room used for TV, sport, gaming, and the occasional movie.
• Cinema (40°): THX's recommended angle for a reference movie experience. It fills more of your vision and calls for a noticeably larger screen at the same seat.

A quick reality check

With 4K TVs you can sit much closer than the old 1080p rules allowed without seeing pixels, so for most rooms the honest advice is: buy the largest screen that fits your wall, your budget, and — for the cinema look — that your seat can support. If two people disagree, the mixed-use figure is the safe floor and the cinema figure is the aspirational ceiling.

Frequently asked questions

Can a TV be too big for a room? For picture quality on a 4K set, rarely — you would have to sit close enough to see individual pixels, which is closer than most people sit. The real limits are the size of your wall, the viewing angle from off-centre seats, and neck comfort if you sit very close to a very large screen.

Should I measure to the couch or the back of the room? Measure to where you actually sit most of the time. If seating is spread out, use the primary seat; a screen sized for the closest seat will still look good from further back, just smaller.

Does this depend on resolution? The recommended size here is about how big the screen looks, not how sharp it is. On a 4K TV you can comfortably go to the cinema (40°) figure; on an older 1080p set you may prefer the mixed-use (30°) figure so you sit far enough back that the pixels aren't visible.

What about an ultrawide or 21:9 screen? These figures assume a standard 16:9 TV. A 21:9 screen of the same diagonal is wider and shorter, so it fills a different viewing angle — treat the result as a rough guide only.

These are planning estimates based on published viewing-angle guidance. See our electrical and lighting guides for mounting height and glare tips once you've picked a size.