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Aspect Ratio Calculator

This aspect ratio calculator reduces any width and height to a simple ratio (1920x1080 is 16:9) and solves for a missing dimension when you resize, with presets for video, photo, phone, and ultrawide.

What do you want?

Presets

Pixels or any unit. 1920 and 1080 become 16:9.

Examples

Aspect ratio

16:9

Simplified ratio
16:9
Greatest common divisor
120
Width ÷ height
1.7778
Preset
16:9

1,920 and 1,080 divided by 120.

The math stays in your browser. Nothing you type is uploaded.

How to use

  1. Enter a width and a height, or pick a preset: 16:9, 4:3, 1:1, 9:16, 21:9, or 3:2.
  2. Read the simplified ratio. Both numbers are divided by their greatest common divisor.
  3. To resize, enter a new width or a new height. The other dimension keeps the same ratio.
  4. Use 9:16 for a vertical phone video and 21:9 for an ultrawide screen.

Formula

The greatest common divisor of the two sizes is found with Euclid's algorithm. The simple ratio is each size divided by that divisor. A new height is new width times original height divided by original width. A new width is new height times original width divided by original height.

Example. 1920 by 1080 has a greatest common divisor of 120, so the ratio is 16:9. A new width of 1,280 at 16:9 has a height of 720.

Example. 1080 by 1920 simplifies to 9:16. A 21:9 frame that is 2,560 wide is 1,097.1429 tall.

Frequently asked questions

What is aspect ratio?

The proportion of width to height, such as 16:9 for HD video.

How do I find the aspect ratio of 1920x1080?

Divide both numbers by their greatest common divisor (120) to get 16:9.

How do I resize and keep the ratio?

New height = new width x original height / original width.

What ratio is a vertical phone video?

9:16, which is 16:9 turned on its side.

What is 21:9?

An ultrawide ratio used for cinema-style monitors and some films.

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