Display size

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 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.

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) larger.

Liquid crystal displays use 100% of their surface to display, thus the VIS is the actual size presented to the viewer.

In the U.S., manufacturers and retailers are allowed to list the tube size, which is misleading and confusing to many customers, especially when comparing both CRT and LCD models together. In many other countries, this practice is prohibited by consumer-protection laws.

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 widescreens than compared to more rectangular 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:

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

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

, 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.

Width, height and viewable area from diagonal measurement and aspect ratio, rounded to centimetres

Diagonal			5:4				4:3				8:5				16:9
(in)	(cm)		w (cm)	h (cm)	A (cm²)		w (cm)	h (cm)	A (cm²)		w (cm)	h (cm)	A (cm²)		w (cm)	h (cm)	A (cm²)
7	18		14	11	154		14	11	152		15	9	142		15	9	135
10	25		20	16	315		20	15	310		22	13	290		22	12	264
11	28		22	17	381		22	17	375		24	15	351		24	14	334
14	36		28	22	617		28	21	607		30	19	568		31	17	527
15	38		30	24	708		30	23	697		32	20	652		33	19	620
17	43		34	27	910		35	26	895		37	23	838		38	21	797
19	48		38	30	1136		39	29	1118		41	26	1047		42	24	995
20	51		40	32	1259		41	30	1239		43	27	1160		44	25	1103
21	53		42	33	1388		43	32	1366		45	28	1279		46	26	1216
22	56		44	35	1523		45	34	1499		47	30	1403		49	27	1334
23	58		46	36	1665		47	35	1638		50	31	1534		51	29	1458
24	61		48	38	1813		49	37	1784		52	32	1670		53	30	1588
25	64		50	40	1967		51	38	1935		54	34	1812		55	31	1723
26	66		52	41	2127		53	40	2093		56	35	1960		58	32	1864
27	69		54	43	2294		55	41	2258		58	36	2114		60	34	2010
28	71		56	44	2467		57	43	2428		60	38	2273		62	35	2161
29	74		58	46	2647		59	44	2604		62	39	2439		64	36	2318
30	76		60	48	2832		61	46	2787		65	40	2610		66	37	2481
31	79		61	49	3024		63	47	2976		67	42	2787		69	39	2649
32	81		63	51	3223		65	49	3171		69	43	2969		71	40	2823
33	84		65	52	3427		67	50	3372		71	44	3158		73	41	3002
34	86		67	54	3638		69	52	3580		73	46	3352		75	42	3187
35	89		69	56	3855		71	53	3794		75	47	3552		77	44	3377
36	91		71	57	4079		73	55	4013		78	48	3758		80	45	3573
37	94		73	59	4308		75	56	4239		80	50	3970		82	46	3774
38	97		75	60	4544		77	58	4472		82	51	4187		84	47	3981
39	99		77	62	4787		79	59	4710		84	53	4410		86	49	4193
40	102		79	63	5035		81	61	4955		86	54	4639		89	50	4411
41	104		81	65	5290		83	62	5206		88	55	4874		91	51	4634
42	107		83	67	5552		85	64	5463		90	57	5115		93	52	4863
43	109		85	68	5819		87	66	5726		93	58	5361		95	54	5097
44	112		87	70	6093		89	67	5995		95	59	5614		97	55	5337
45	114		89	71	6373		91	69	6271		97	61	5872		100	56	5582
46	117		91	73	6659		93	70	6553		99	62	6136		102	57	5833
47	119		93	75	6952		96	72	6841		101	63	6405		104	59	6090
48	122		95	76	7251		98	73	7135		103	65	6681		106	60	6352
49	124		97	78	7556		100	75	7435		106	66	6962		108	61	6619
50	127		99	79	7868		102	76	7742		108	67	7249		111	62	6892

The aspect ratio of 5:3 is found on several smartphones, such as those having a screen resolution of 480x800 pixels:

Diagonal			5:3
(in)	(cm)		w (cm)	h (cm)	A (cm²)
3.5	8.9		4.6	7.6	35
3.7	9.4		4.8	8.1	39
4	10.2		5.2	8.7	46
4.3	10.9		5.6	9.4	53
5	12.7		6.5	10.9	71