Wall unit depths and TV sizes: the niche, the shelf and the distance to the sofa

Screen sizes in millimetres

Inches describe the diagonal, and a niche is drawn in width and height, so start from a specification sheet. One maker's 2024 range, without its stand, measures as follows. A second maker's 65 inch OLED from the same year is 1441 by 826 mm but 45 mm deep, because the panel and its electronics are built differently, and weighs 16.6 kg.

Sources: Samsung Australia: QN90D Neo QLED 4K (2024), retailer specification sheet, LG UK: 65 inch OLED evo C4 (2024), specifications

The niche: air, and the next TV

The same maker's mounting guide says the top, bottom and sides of the set should be at least 10 cm from other objects for ventilation, and that the TV should go on a solid wall perpendicular to the floor. So a niche for a 65 inch set is at least 1650 by 1030 mm, and that is before you think about the set you will buy in five years.

Our reference living room wall unit has a niche of 1800 by 1450 mm. It was drawn for a 55 inch set and sized for a 75 inch one at 1680 by 965 mm, with the air around it and a shelf under it for the soundbar. Draw the niche for the bigger screen and the smaller one simply sits in more wall. The other way round means a saw.

Source: Samsung UK support: How to mount your TV on a wall or stand

Why 300 mm deep

Our wall units are built as closed boxes 300 mm deep, with shelves and dividers at 290 mm so they stop 10 mm short of the wall and sit flush at the front. That depth holds books, a receiver and a router, and it holds the TV. A slim wall mount places a set about 55 mm from the wall, and the screens above are 27 to 45 mm deep, so the back of the TV and its plugs sit within the depth of the shelves beside it.

A full motion arm is another matter. One maker's arm for 42 to 90 inch sets, carrying up to 56.7 kg, folds to 55 mm from the wall and extends to 711 mm, and takes hole patterns from 200 by 200 to 600 by 400 mm. If you want the screen to swing towards the dining table, the niche needs clear sides and the arm's plate needs solid fixing behind the back panel.

Source: Sanus: VLF728 full motion wall mount for 42 to 90 inch TVs, specifications

The shelf under the TV

A soundbar wants to sit just under the screen, on the shelf or on the console. One current soundbar is 75 mm high, 1178 mm wide and 111 mm deep and weighs 5.9 kg. So the gap between the bottom of the screen and the shelf wants about 150 mm, and the shelf itself has to be at least that wide. A console shelf that also carries a receiver and a games console wants 36 mm of board, not 18, which is how our wall units build every open shelf: two 18 mm boards glued face to face, banded on the front edge.

Long spans get steel. A TV shelf or a shelf over 1200 mm has two steel flat bars of 30 by 10 mm bedded in grooves between the layers, so it stays straight for the life of the unit.

Source: Sonos: Arc Ultra soundbar, dimensions

How high, and how far

One mount maker's guidance is that the ideal TV height is centred at eye level, which averages 42 inches when seated, or about 1070 mm. In our reference room the screen centre sits at 1300 mm, about four degrees above eye level from a sofa 4 m away, because the console under it carries a soundbar and the family watches from a deep seat. Sit on your sofa, measure your eye height, and give us that number.

For distance, two widely quoted rules come from cinema bodies, as summarised in the encyclopaedia article on the subject. THX guidance puts the screen at about 40 degrees of view, which works out at a distance of about 1.2 times the diagonal. The 30 degree figure usually attributed to SMPTE works out at about 1.6 times the diagonal, though the article notes there is no direct SMPTE recommendation. At 4 m that points to a screen of 98 inches on the 30 degree rule and far larger on the THX rule, which is why most living rooms end up with the biggest set the wall and the budget allow, and why the niche should be drawn for the bigger one.

Source: Sanus: HeightFinder, TV mounting height

Books, and what a shelf can span

Books are heavy. The North American panel association's shelving bulletin gives 19 mm particleboard and MDF a single span of roughly 510 to 580 mm at its heaviest listed load, about 2.4 kilopascals, with a sag limit of the span divided by 240. A 900 mm bookshelf in a single 18 mm board is outside that, which is why every open shelf in our wall units is doubled to 36 mm and anything long carries steel. For a wardrobe shelf of folded clothes the same table is generous, see wardrobe internals by width.

Source: Composite Panel Association: Particleboard and MDF for shelving, technical bulletin

Cables, sockets and the tech box

Decide where the TV, the receiver and the soundbar go, then put sockets where the plugs will be: behind the TV, inside the console, and one at worktop height for a lamp. A 50 mm tube inside the wall from the TV down to the console lets you pull a new cable through in five years without opening anything. The LED drivers and the router live in a ventilated cupboard with a fixed shelf, and an electrician confirms the circuits. The unit stands on its plinth and is screwed to the wall against tipping, two screws per open cell into a stud or a plywood strip, never into plasterboard alone.

More layouts and finishes are in TV wall unit ideas. When you have your sofa distance, your eye height and the TV you might buy, start on our page for wall units.

Source: Wikipedia: Optimum HDTV viewing distance (THX and SMPTE guidance, summarised)