# Display size

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Diagram comparing various typical screen sizes by width, height, diagonal, area and aspect ratio.

On two-dimensional display devices such as computer monitors and television sets, the display size (or viewable image size or VIS) is the actual amount of screen space that is available to display a picture, video or working space, without obstruction from the case or other aspects of the unit's design. The viewable image size (often measured in inches or millimeters) is sometimes called the physical image size, to distinguish it from the "logical image size" (display resolution, measured in pixels) of various computer display standards.

The size of an approximately rectangular display is usually given by TV and monitor manufacturers as the distance between two opposite screen corners, that is, the diagonal of the rectangle. This method of measurement is inherited from the method used for the first generation of CRT television, when picture tubes with circular faces were in common use. Being circular, only their diameter was needed to describe their size. Since these circular tubes were used to display rectangular images, the diagonal measurement of the rectangle was equivalent to the diameter of the tube's face. This method continued even when cathode ray tubes were manufactured as rounded rectangles; it had the advantage of being a single number specifying the size, and was not confusing when the aspect ratio was universally 4:3. In the US, when virtually all TV tubes were 4:3, the size of the screen was given as the diagonal with a V following it. In Japan and other markets, the size of the outer diameter of the tube was given. What was a 27V in the US would be a 28" in Japan. However the V terminology was frequently dropped in US advertising referring to a 27V as a 27". This was not misleading for the consumer as the seller had to give the actual screen size by law. Liquid crystal displays use 100% of their surface to display, thus the VIS is the actual size presented to the viewer.

A problematic practice was the use of the size of a monitor's imaging element, rather than the size of its viewable image, when describing its size in publicity and advertising materials. On CRT displays a substantial portion of the CRT's screen is concealed behind the case's bezel or shroud in order to hide areas outside the monitor's "safe area" due to overscan. These practices were seen as deceptive, and widespread consumer objection and lawsuits eventually forced most manufacturers to instead measure viewable size[citation needed]. On cathode ray tube monitors, VIS differs noticeably from the full tube size, which is generally about 25 mm (1 in).

When the common aspect ratio went from 4:3 to 16:9, the new widescreens were labeled with a W. A screen that is approximately the same height as a 27V would be a 32W. Recently Vizio and other US TV manufacturers have introduced even wider screens with a 21:9 aspect ratio in order to match aspect ratios used in cinemas. In order to gauge the relative sizes of these new screens, the screen aspect must be considered. Indeed, in a commercial market where multiple aspect ratios are being sold, it will always take two numbers to describe the screen size, some combination of diagonal, aspect ratio, height or width.

Set sizes are frequently given as a "class" as screens from different manufacturers will have slight differences in size. However the "class" should be within 1/2" of the actual size. The reasons for the different sizes within a class stem from differences in the manufacturers' equipment. LCDs are cookie-cut from one large piece of glass. As manufacturers move from one size to another, newer larger sizes must fit on the same size glass, though with fewer displays being cut from it. Some sizes fit well and maximize glass utilization, other sizes fit more poorly and waste glass. As an example, in some cases, increasing the screen size by even 0.1" can cause an LCD manufacturer to go from 12 screens fitting on their glass sheet to 9. This would make them uncompetitive with other screen makers.

Ideal Screen Size

The TV image is composed of many lines of pixels. Ideally, the TV watcher sits far enough away from the screen that the individual lines merge into one solid image. The watcher may sit even farther away and still see a good picture, but it will be a smaller portion of their visual field. The resolution of the human eye (with 20/20 vision) is about one minute of arc. For full HDTV resolution, this one minute of arc implies that the TV watcher should sit 4 times the height of the screen away. So the ideal set size may be determined from the chart below by measuring the distance from where the watcher would sit to the screen in inches, dividing that by 4, and comparing with the screen heights below. If the user is replacing a standard definition TV with an HDTV this implies that the best visual experience will be with a set that is twice as tall as the standard definition set. As the average size LCD TV being sold is now 38", which is only about 15% taller than their old 27V, this means that most consumers buy HDTV sets that are smaller than what they could utilize. Of course, in addition to screen size, budget sizes must be considered as well.

## Measurements and units

The practice of measuring display devices by the diagonal is a remnant from the time when cathode ray tubes were used, which basically created circular projections, and any rectangular area derived thereof had a diagonal equal to the circle diameter.

The main measurements for display devices are:

• Width and height
• Total area
• The diagonal, usually measured in inches. The diagonal measurement of a display as the actual viewable area is also dependent on the aspect ratio of the display. For a display device of the same area, the diagonal achieves a larger value in a widescreen than compared to a more square screen. There is a risk of manufacturers making displays wider than what is actually most convenient in order to make the diagonal achieve a larger value.

### Conversion equations

The width and height can be calculated from the diagonal as follows:

$height=D \times \sqrt{\frac{H^2}{W^2+H^2}}$

$width=\frac{W}{H} \times height$

, where:

• D is the diagonal
• W and H are taken from the aspect ratio as W:H, or, alternatively, by the screen resolution given by rows of pixels (assuming square-shaped pixels).

### Conversion charts

These are charts of some common sizes of LCDs with varying aspect ratios and their actual viewable area.

Diagonal 5:4 4:3 16:10 5:3 (15:9) 16:9 (in) (cm) w (cm) h (cm) A (cm²) w (cm) h (cm) A (cm²) w (cm) 7 6 39 7 5 38 8 5 36 8 5 35 8 4 34 7 6 43 8 6 42 8 5 40 8 5 39 8 5 38 8 6 50 8 6 50 9 5 46 9 5 46 9 5 44 9 7 58 9 7 57 9 6 54 9 6 53 10 5 51 10 8 79 10 8 77 11 7 72 11 7 71 11 6 69 14 11 154 14 11 152 15 9 142 15 9 139 15 9 135 20 16 315 20 15 310 22 13 290 22 13 285 22 12 276 23 18 423 24 18 417 25 16 390 25 15 383 26 14 371 26 21 557 27 20 548 29 18 513 29 17 503 29 17 488 28 22 617 28 21 607 30 19 568 30 18 558 31 17 540 30 24 708 30 23 697 32 20 652 33 20 640 33 19 620 31 24 746 31 23 734 33 21 688 34 20 675 34 19 654 34 27 910 35 26 895 37 23 838 37 22 823 38 21 797 37 29 1077 38 28 1060 40 25 992 40 24 974 41 23 944 38 30 1136 39 29 1118 41 26 1047 41 25 1028 42 24 995 40 32 1259 41 30 1239 43 27 1160 44 26 1139 44 25 1103 42 33 1388 43 32 1366 45 28 1279 46 27 1255 46 26 1216 44 35 1523 45 34 1499 47 30 1403 48 29 1378 49 27 1334 46 36 1665 47 35 1638 50 31 1534 50 30 1506 51 29 1458 48 38 1813 49 37 1784 52 32 1670 52 31 1639 53 30 1588 50 40 1967 51 38 1935 54 34 1812 54 33 1779 55 31 1723 52 41 2127 53 40 2093 56 35 1960 57 34 1924 58 32 1864 54 43 2294 55 41 2258 58 36 2114 59 35 2075 60 34 2010 56 44 2467 57 43 2428 60 38 2273 61 37 2231 62 35 2161 58 46 2647 59 44 2604 62 39 2439 63 38 2394 64 36 2318 60 48 2832 61 46 2787 65 40 2610 65 39 2562 66 37 2481 61 49 3024 63 47 2976 67 42 2787 68 41 2735 69 39 2649 63 51 3223 65 49 3171 69 43 2969 70 42 2915 71 40 2823 77 62 4787 79 59 4710 84 53 4410 85 51 4329 86 49 4193 83 67 5552 85 64 5463 90 57 5115 91 55 5021 93 52 4863 99 79 7868 102 76 7742 108 67 7249 109 65 7116 111 62 6892 109 87 9520 112 84 9368 118 74 8771 120 72 8610 122 68 8339 115 92 10587 118 88 10418 125 78 9754 126 76 9575 128 72 9274 119 95 11330 122 91 11148 129 81 10439 131 78 10247 133 75 9924 127 102 12891 130 98 12684 138 86 11877 139 84 11658 142 80 11292 139 111 15421 142 107 15174 151 94 14208 152 91 13947 155 87 13508 159 127 20142 163 122 19819 172 108 18557 174 105 18216 177 100 17643 167 133 22206 171 128 21851 181 113 20460 183 110 20083 186 105 19452 196 157 30845 201 151 30351 213 133 28419 216 129 27897 219 123 27019 202 162 32743 207 155 32219 220 137 30167 222 133 29613 226 127 28681 214 171 36708 219 165 36121 233 145 33821 235 141 33199 239 134 32155 220 176 38776 226 169 38155 239 149 35726 242 145 35069 246 138 33966 301 241 72711 309 232 71548 327 205 66992 331 199 65761 336 189 63692