Why an 85-inch screen is not 85 inches wide
The number on the box is the diagonal, corner to corner. The width follows from the shape: on a 16:9 panel the diagonal is 2.0397 times the height, so 85 inches of diagonal leaves 41.6722 inches of height and 74.0839 inches of width. Shown to two decimals that is 74.08 by 41.67 inches, or 188.17 by 105.85 cm, and the glass covers 3,087.2 square inches — 19,918 square centimetres.
Change the shape and the same diagonal spreads differently. An 85-inch 21:9 panel is 78.13 inches wide but only 33.48 inches tall: 4.04 inches wider, 8.19 inches shorter and 15.3% less glass. An 85-inch 4:3 panel lands on exactly 68 by 51 inches. Same number on the box, three different pieces of wall.
Where the extra 0.8 inches comes from
Every figure published for this size sits inside one narrow band, 74.0 to 74.8 inches — 0.8 inch from end to end. The panel is 74.08. Four numbers, four different reasons, and none of them is a tolerance:
74.0 — the decimal cut off. 74.0839 truncated at the point instead of rounded: 0.08 in short of the glass.
74.1 — rounded to one decimal. 74.0839 rounds down to 74.1, which is 0.02 in over. This one is the panel, said to the nearest tenth.
189 cm — rounded to the whole centimetre. The width is 188.17 cm. Written as 188 cm the figure is 74.02 in; written as 189 cm it is 74.41 in, which is 0.33 in over the glass. One centimetre is 0.39 in, so at this size a whole-centimetre figure is allowed to be nearly half an inch wrong.
74.8 — the shortcut multiplier. On a 16:9 panel the width is 0.8716 of the diagonal, and the usual shortcut rounds that to 0.88: 0.88 × 85 = 74.80 exactly. The result above prints that line for you at whatever diagonal you type.
The interesting one is 74.8, because it comes with a height. 43.1 in is published next to it, and the height shortcut is only 42.50, so the shortcut leaves 0.6 in of that height unexplained. Measured against the glass instead of the shortcut, 74.8 is 0.72 in wider than 74.08 and 43.1 is 1.43 in taller than 41.67. A frame accounts for both: 0.36 in of bezel on each side takes 74.08 to 74.80, and 0.71 in at the top and the bottom takes 41.67 to 43.10. Sets put more of that height in the bottom chin than above the glass, which is why the vertical excess runs about twice the horizontal one.
That reading is an inference from the arithmetic, and this page cannot prove which of the two roads a given listing took, because 0.88 × 85 and a 0.36-inch frame both arrive at 74.80. The height is the only place they separate. What is certain is the glass: 74.08 by 41.67 inches, one width, no band. Everything in that 0.8-inch spread is either that number rounded, that number converted badly, or something that measures more than the lit panel.
Width and height by size
These are the 16:9 figures for the sizes sold most often. Bezel and stand are not included, so a real set is a little wider than the number here.
| Diagonal | Width | Height | Area |
|---|---|---|---|
| 55 in | 47.94 in / 121.8 cm | 26.96 in / 68.5 cm | 1,293 sq in |
| 65 in | 56.65 in / 143.9 cm | 31.87 in / 80.9 cm | 1,805 sq in |
| 75 in | 65.37 in / 166.0 cm | 36.77 in / 93.4 cm | 2,404 sq in |
| 85 in | 74.08 in / 188.2 cm | 41.67 in / 105.8 cm | 3,087 sq in |
| 98 in | 85.41 in / 217.0 cm | 48.05 in / 122.0 cm | 4,104 sq in |
The sizes below this one have their own pages: how wide is a 75 inch tv gives 65.37 by 36.77 inches, how wide is a 65 inch tv gives 56.65 by 31.87, and how wide is a 50 inch tv gives 43.58 by 24.51. Where to put the seat is a different question, and that one is worked out here.
How the numbers are calculated
Everything comes from the diagonal and the ratio, so nothing is looked up:
height = diagonal ÷ √((a ÷ b)² + 1)
width = (a ÷ b) × height
area = width × height
centimetres = inches × 2.54
square centimetres = square inches × 6.4516
diagonal in pixels = √(pixels wide² + pixels high²)
PPI = diagonal in pixels ÷ diagonal in inches
The ratio a:b is the width over the height, so 16:9 means 16 units across for every 9 down. For 85 inches at 16:9 the divisor is √((16 ÷ 9)² + 1) = 2.039729, and 85 ÷ 2.039729 = 41.6722. The pixel rows only run when a resolution is chosen; they do not change the width, the height or the area.
What is rounded
Width and height are shown to 2 decimals in inches and 1 decimal in centimetres, area to the nearest square inch with a thousands separator, and the centimetre area to the nearest square centimetre. PPI is shown to 1 decimal. The arithmetic runs at full precision and only the display is rounded, so a difference that reads as 0.00 at the shown precision is still a real difference in the panel.
The whole-inch line under the results is a separate calculation, not a rounding of the displayed figures: it takes the exact width and height up to the next whole inch, which is what whole-number listings do, and reports how far above the panel that lands. On a 16:9 panel it also prints the two shortcut multipliers, 0.88 × diagonal and diagonal ÷ 2, so you can tell which figure a listing used.
What is measured
These are the active panel measurements: the lit rectangle you watch. Bezels, the frame around the glass, the stand and the depth of the chassis are all excluded, so an 85-inch set will measure wider than 74.08 inches once you include the frame. Wall space is the width figure, because the panel is mounted flat; add clearance for the mount if it tilts. Check the stud spacing before anything else at this size: 74.08 inches of panel usually spans more than two studs.
Questions this page answers
So how wide is an 85-inch TV really?
74.08 inches across the glass, or 188.2 cm, for a 16:9 panel. The 85 is the diagonal, not the width.
Is 74.8 inches the same thing?
No, that is the panel plus something. 0.88 × 85 = 74.80 is the shortcut multiplier, and a frame about 0.36 in per side lands on the same number. Either way the glass is 74.08.
How tall is it?
41.67 inches, or 105.8 cm, at 16:9. The 21:9 version of the same diagonal is 78.13 in wide and 33.48 in tall.
Will it fit in my alcove?
Compare your gap with 74.08 inches, then add the frame on both sides and a little room to lift it onto the mount. At this width the frame alone can add most of an inch.
How much area is that, and how much more is a 98?
3,087.2 square inches at 16:9, which is 19,918 square centimetres. A 98-inch panel covers 4,104 square inches, 33% more glass for 15% more diagonal.
Does 4K change any of these numbers?
No. Resolution changes only the pixel rows: 4,406 pixels on the diagonal, 51.8 PPI, 0.490 mm per pixel at 85 inches. Width, height and area stay exactly where they were.
Is the 85 measured across the glass or the whole set?
Across the glass, corner to corner, with the frame excluded. That is why a set sold as 85 inches measures wider than 74.08 inches once you put a tape on the outside.