Aspect ratio

This article is about shapes. For the aspect ratio of images, film and video, see Aspect ratio (image).

The aspect ratio is the ratio of the width of a shape to its height when the width is larger than the height, i.e. the shape is positioned as a "landscape" rather than "portrait".

The aspect ratio is expressed as two numbers separated by a colon (x:y). A common misunderstanding is that x and y represent actual length and height. This is false; they actually represent the relation between width and height. As an example, 8:5, 16:10 and 1.6:1 are the same aspect ratio.

It may be applied to two characteristic dimensions of a three-dimensional shape.

Applications and uses

The term is most commonly used with reference to:

• Graphic / image
  • Image aspect ratio
  • Display aspect ratio: the aspect ratio for computer displays.
  • Paper size
  • Standard photographic print sizes
  • 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 structures without slant
• Tire code
• Tire sizing
• wing aspect ratio of an aircraft or bird
• Astigmatism of an optical lens

Examples

Rectangles

Main article: Aspect ratio (image)

For a rectangle, the aspect ratio denotes the ratio of length to width of the rectangle. An aspect ratio of 1:1 is a square.

From left to right:

When comparing the above illustration to the below text, please note that the above x:y aspect ratio values are shown as vertical orientation rectangles to better demonstrate visual differences, whereas the aspect ratio values of the text below are written as rotated horizontal orientation rectangles (e.g. compare 3:4 vertical orientation illustration to 4:3 horizontal orientation text).

• 4:3 = 1.3: Some (not all) 20th century computer monitors (VGA, XGA, etc.), standard-definition television
• √2:1 = 1.414…: International paper sizes (ISO 216)
• 3:2 = 1.5: 35mm still camera film, iPhone displays
• 16:10 = 1.6 (not shown above): Commonly used widescreen computer displays (WXGA)
• Φ:1 = 1.618…: Golden ratio, close to 16:10
• 5:3 = 1.6: Super 16 mm, a standard film gauge in many European countries
• 16:9 = 1.7: Widescreen TV

Ellipses

For an ellipse, the aspect ratio denotes the ratio of the major axis to the minor axis. An aspect ratio of 1:1 is a circle.

Math and aspect ratio

Aspect ratios are mathematically expressed as x:y (pronounced "x-to-y") and x×y (pronounced "x-by-y"), with the latter particularly used for pixel dimensions, such as 640×480. 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 images there is a subtle distinction between the Display Aspect Ratio (the image as displayed) and the Storage Aspect Ratio (the ratio of pixel dimensions); see distinctions, below.

See also

• Ratio
• Equidimensional ratios in 3D
• Vertical orientation