Quick answer

Aspect ratio compares width with height. A 16:9 image is 16 units wide for every 9 units high, whether its pixel dimensions are 1920 by 1080 or 1280 by 720.

Original example

The same shape at two sizes

A 1920 by 1080 image and a 1280 by 720 image both reduce to 16:9. They contain different numbers of pixels, but their rectangular shape has the same proportions.

Interactive tool

Aspect ratio calculator

Mathematical height

1080 px

Nearest whole-pixel height: 1080 px

Mathematical ratio 16:9

How aspect ratio works

Write width first and height second, separated by a colon. Divide both values by their greatest common divisor to reduce the ratio. A square is 1:1, while 9:16 describes a tall portrait shape.

Ratio describes shape, not image detail. Two files with the same ratio can have very different pixel counts and quality.

Common misunderstandings

  • 16:9 does not mean an image has a specific pixel size.
  • A ratio can describe a portrait, landscape, or square shape.

Related answers

Sources

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