View source for Aspect ratio

{{Short description|Attribute of a geometric shape}}
{{Other uses}}
{{Use dmy dates|date=January 2024}}
{{More citations needed|date=June 2023}}
The '''aspect ratio''' of a [[geometry|geometric]] shape is the [[ratio]] of its sizes in different dimensions. For example, the aspect ratio of a [[rectangle]] is the ratio of its longer side to its shorter side—the ratio of width to height,<ref>{{Cite web|url=http://whatis.techtarget.com/definition/aspect-ratio |title=What is aspect ratio? |first=Margaret |last=Rouse |date=September 2005 |access-date=3 February 2013 |work=WhatIs? |publisher=TechTarget}}</ref><ref>{{Cite web|url=https://e3displays.com/wide-aspect-ratio-display/ |title=Wide aspect ratio display |first=Margaret |last=Rouse |date=September 2002|access-date=18 February 2020|work=display |publisher=E3displays}}</ref> when the rectangle is oriented as a "[[landscape format|landscape]]".

The aspect ratio is most often expressed as two integer numbers separated by a colon (x:y), less commonly as a simple or decimal [[Fraction (mathematics)|fraction]]. The values x and y do not represent actual widths and heights but, rather, the proportion between width and height. As an example, 8:5, 16:10, 1.6:1, {{Frac|8|5}} and 1.6 are all ways of representing the same aspect ratio.

In objects of more than two dimensions, such as [[hyperrectangle]]s, the aspect ratio can still be defined as the ratio of the longest side to the shortest side.

==Applications and uses==
The term is most commonly used with reference to:
* Graphic / image
** [[Aspect ratio (image)|Image aspect ratio]]
** [[Display aspect ratio]]
** [[Paper size]]
** [[Standard photographic print sizes]]
** [[List of film formats|Motion picture film formats]]
** [[Standard ad size]]
** [[Pixel aspect ratio]]
** [[Photolithography]]: the aspect ratio of an etched, or deposited structure is the ratio of the height of its vertical side wall to its width.
* [[HARMST]] High Aspect Ratios allow the construction of tall microstructures without slant
* [[Tire code]]
* [[Tire sizing]]
* [[Turbocharger]] impeller sizing
* [[Aspect ratio (wing)|Wing aspect ratio]] of an aircraft or bird
* [[Astigmatism (optical systems)|Astigmatism]] of an [[optical lens]]
* Nanorod dimensions
* [[Shape factor (image analysis and microscopy)]]
* [[Finite Element Analysis]]
* Flag design; see [[List of aspect ratios of national flags]]

==Aspect ratios of simple shapes==
===Rectangles===
{{Main|Aspect ratio (image)}}
For a rectangle, the aspect ratio denotes the ratio of the width to the height of the rectangle. A [[square]] has the smallest possible aspect ratio of 1:1.

Examples:
* 4:3 = 1.{{overline|3}}: Some (not all) 20th century computer monitors ([[VGA]], [[XGA]], etc.), [[standard-definition television]]
* <math>\sqrt{2}:1 = 1.414...</math>: international paper sizes ([[ISO 216]])
* 3:2 = 1.5: [[135 film|35mm still camera film]], [[iPhone#Models|iPhone]] (until [[iPhone 5]]) displays
* [[16:10]] = 1.6: commonly used [[widescreen]] [[computer display]]s ([[WXGA (graphics)|WXGA]])
* Φ:1 = 1.618...: [[golden ratio]], close to 16:10
* 5:3 = 1.{{overline|6}}: [[super 16 mm]],  a standard [[film gauge]] in many European countries
* 16:9 = 1.{{overline|7}}: [[widescreen]] TV and most laptops
* 2:1 = 2: [[Domino (mathematics)|dominoes]]
* 64:27 = 2.{{overline|370}}: ultra-widescreen, [[21:9 aspect ratio|21:9]]
* 32:9 = 3.{{overline|5}}: super ultra-widescreen

===Ellipses===
For an ellipse, the aspect ratio denotes the ratio of the [[major axis]] to the [[minor axis]]. An ellipse with an aspect ratio of 1:1 is a circle.
[[File:Elps-slr.svg|center|500px]]

==Aspect ratios of general shapes==
In [[geometry]], there are several alternative definitions to aspect ratios of general [[compact set]]s in a d-dimensional space:<ref name=SmithWormald1998>{{Cite book
| last1 = Smith | first1 = W. D.
| last2 = Wormald | first2 = N. C.
| doi = 10.1109/sfcs.1998.743449
| chapter = Geometric separator theorems and applications
| title = Proceedings 39th Annual Symposium on Foundations of Computer Science (Cat. No.98CB36280)
| pages = 232
| year = 1998
| isbn = 0-8186-9172-7
| s2cid = 17962961
| url = http://users.monash.edu.au/~nwormald/papers/geomsep.ps.gz
}}</ref>
* The diameter-width aspect ratio (DWAR) of a compact set is the ratio of its diameter to its width. A circle has the minimal DWAR which is 1. A square has a DWAR of <math>\sqrt{2}</math>.
* The cube-volume aspect ratio (CVAR) of a compact set is the ''d''-th root of the ratio of the ''d''-volume of the smallest enclosing axes-parallel ''d''-cube, to the set's own ''d''-volume. A square has the minimal CVAR which is 1. A circle has a CVAR of <math>\sqrt{2}</math>. An axis-parallel rectangle of width ''W'' and height ''H'', where ''W''&gt;''H'', has a CVAR of <math>\sqrt{W^2/WH} = \sqrt{W/H}</math>.

If the dimension ''d'' is fixed, then all reasonable definitions of aspect ratio are equivalent to within constant factors.

==Notations==
Aspect ratios are mathematically expressed as ''x'':''y'' (pronounced "x-to-y").

Cinematographic aspect ratios are usually denoted as a (rounded) decimal multiple of width vs unit height, while photographic and videographic aspect ratios are usually defined and denoted by whole number ratios of width to height. In [[digital image]]s there is a subtle distinction between the ''display'' aspect ratio (the image as displayed) and the [[Storage aspect ratio|''storage'' aspect ratio]] (the ratio of pixel dimensions); see [[Aspect ratio (image)#Distinctions|Distinctions]].

==See also==
* [[Axial ratio]]
* [[Ratio]]
* [[Equidimensionality|Equidimensional]] ratios in 3D
* [[List of film formats]]
* [[Squeeze mapping]]
* [[Scale (ratio)]]
* [[Vertical orientation]]

==References==
{{Reflist}}

{{Fractions and ratios}}

{{DEFAULTSORT:Aspect Ratio}}
[[Category:Ratios]]