Aspect Ratio

What is "Aspect Ratio" in a Screen, Image, or Video?

Aspect ratio (abbreviated AR) is a term meaning the ratio between the width and the height of a screen, image, or video. For example, if an image has the dimensions 1600x900px (1600 pixels of width by 900 pixels of height), its aspect ratio is 1600:900. This colon symbol (:) means ratio in the mathematical sense. We can simplify this ratio just like any mathematical operation of division: 1600 divided by 900 is the same thing as 16 divided by 9, therefore 1600:900 equals 16:9. If we divide 16 by 9, we get the value 1.777777777... We can say the aspect ratio of the image is 16:9 or 1.77~.

Using the rule of three, we can obtain a dimension of the image using the aspect ratio and the other dimension.

For example, say we have an image of 1600 pixels of width by 900 pixels of height (ratio 1.77~). We want to resize the image to half its size (800x450). It's possible to calculate this 450 from the 800, or vice-versa, through the following formula:

new height = new width  × height ÷ width
new width  = new height × width  ÷ height

Or more directly:

new height = new width ÷ aspect ratio
new width  = new height × aspect ratio

In this case:

450 = 800 ×  900 ÷ 1600
800 = 450 × 1600 ÷  900
450 = 800 ÷ 1.777777...
800 = 450 × 1.777777...

Some aspect ratios:

• 4:3 (1.33~), e.g. 640x480, 800x600, 1028x768.
• 16:9 (1.77~), e.g. 853x480, 1280x720, 1366x768, 1600x900, 1920x1080.
• 1:1 (1), e.g. 256x256, 512x512.

Note: the terms 480p, 720p, and 1080p generally refer to resolutions with the respective widths in the aspect ratio 16:9.