Why a 75-inch screen is not 75 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 75 inches of diagonal leaves 36.7696 inches of height and 65.3682 inches of width. Shown to two decimals that is 65.37 by 36.77 inches, or 166.04 by 93.39 cm, and the glass covers 2,403.6 square inches — 15,507 square centimetres.
Change the shape and the same diagonal spreads differently. A 75-inch 21:9 panel is 68.94 inches wide but only 29.54 inches tall: 3.57 inches wider, 7.23 inches shorter and 15.3% less glass. A 75-inch 4:3 panel lands on exactly 60 by 45 inches. Same number on the box, three different pieces of wall.
Why public numbers for the same screen do not agree
Ask around how wide a 75-inch 16:9 screen is and the answers land between 65.35 in and 66 in for the width, and between 36.8 in and 37.5 in for the height. The panel is one size, so the spread is bookkeeping, not manufacturing. Three habits account for all of it:
Shortcut multipliers. On a 16:9 panel the width is 0.8716 of the diagonal and the height is 0.4903 of it. Two shortcuts round those to 0.88 and to one half: 0.88 × 75 = 66.00 in and 75 ÷ 2 = 37.50 in. That is where 66 by 37.5 comes from — it is the shortcut, not the panel. Measured against the exact 65.37 by 36.77, the shortcut is 0.63 in wide on the width (0.97%) and 0.73 in on the height (1.99%).
Rounding in centimetres, then converting back. 166 cm is 65.3543 in, which prints as 65.35 in. The exact width is 166.04 cm, so a whole-centimetre figure has already dropped 0.04 cm before anyone converts it.
Including the frame. A figure that takes in the bezel is wider than the lit panel by however thick the frame is on that model. That alone is enough to move the last digit, and it is the reason a set can measure wider on your wall than any panel number says.
This page reports the lit rectangle only, computed from the diagonal and the ratio at full precision and rounded once, at the display. Nothing is looked up, so the number you get is the one the geometry gives.
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 |
|---|---|---|---|
| 43 in | 37.48 in / 95.2 cm | 21.08 in / 53.5 cm | 790 sq in |
| 50 in | 43.58 in / 110.7 cm | 24.51 in / 62.3 cm | 1,068 sq in |
| 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 |
The step below this one, 65 inches, is worked out on how wide is a 65 inch tv, which gives the same three figures for that diagonal with a table from 43 to 85 inches. Comparing two sizes rather than reading one is a different job: 55 vs 65 inch tv keeps both panels editable and splits the area gain from the width gain.
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 75 inches at 16:9 the divisor is √((16 ÷ 9)² + 1) = 2.039729, and 75 ÷ 2.039729 = 36.7696. 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 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 a 75-inch set will measure wider than 65.37 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. Where to put the seat is a different question, and that one is worked out here.
Questions this page answers
So how wide is a 75-inch TV really?
65.37 inches across the glass, or 166.0 cm, for a 16:9 panel. The 75 is the diagonal, not the width.
Why do I keep seeing 66 inches instead?
Because whole-inch figures round up. 66 in is 0.63 in, or 0.97%, wider than the panel. If the figure also takes in the frame, it is wider again.
How tall is it?
36.77 inches, or 93.4 cm, at 16:9. The 21:9 version of the same diagonal is 68.94 in wide and 29.54 in tall.
Will it fit in my alcove?
Compare your gap with 65.37 inches, then add the frame on both sides and a little room to lift it onto the mount. Height matters for where the bracket goes rather than for the wall width.
How much does the screen area come to?
2,403.6 square inches at 16:9, which is 15,507 square centimetres. The 21:9 shape of the same diagonal covers 2,036.6 square inches, about 15% less.
Does 4K change any of these numbers?
No. Resolution changes only the pixel rows: 4,406 pixels on the diagonal, 58.7 PPI, 0.432 mm per pixel at 75 inches. Width, height and area stay exactly where they were.
Is the 75 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 75 inches measures wider than 65.37 inches once you put a tape on the outside.