How to Work Out the Aspect Ratio of an Image or Screen
Aspect ratio is just width compared with height, reduced to its simplest form. Here is how to simplify any pair of dimensions.
What is the Aspect Ratio Calculator?
The calculator divides both dimensions by their greatest common divisor to reduce the ratio to its simplest form. It then checks the result against well-known ratios: 16:9, 4:3, 21:9 and 1:1, and labels anything else as custom.
How to use it
- Enter the width in pixels or any unit.
- Enter the height in the same unit.
- Press Calculate to see the simplified ratio and its common name if it has one.
Worked example
Width 1920, height 1080: the tool gives 16:9 (widescreen).
What is the aspect ratio of a 1920 by 1080 screen?
It is 16:9. Both numbers divide by their greatest common divisor, 120, giving 16 and 9, and 16:9 is the standard widescreen ratio used by most modern displays and videos.
Frequently asked questions
Do width and height need to be in pixels?
No. Any consistent unit works, since only the relationship between the two numbers matters.
What does a custom ratio mean?
It simply means the simplified ratio is not one of the famous ones listed. It is still a valid aspect ratio, just less common.