- Aspect ratio measures the relationship between the width and height of a display, sensor, or image.
- A common aspect ratio is 16:9, which means it's 16 units wide and 9 units high.
- There are many aspect ratios in common use today, and each aspect ratio typically has a specific purpose.
Aspect ratio refers to the relationship between something's width and height, and is commonly used to describe computer and TV displays, camera sensors, printed and digital images, and more.
There are many common aspect ratios in use today — for example, many movies are produced in 16:9, and that aspect ratio has become popular among computer displays as well. But that's in sharp contrast to early televisions, which had a 4:3 aspect ratio.
How to measure aspect ratio
Simply put, the aspect ratio is the ratio of width and height, in which the width is usually the first number and the height is the second number. A 16:9 display could be 16 inches long and 9 inches high, or 32 inches long and 18 inches high. Aspect ratio is just that — a ratio — and independent of actual size.
These days, TVs are mostly commonly made with 16:9 displays. Wachirawut Priamphimai / EyeEm/Getty Images
You will occasionally find aspect ratio indicated as a single number, such as 1.33 or 1.78. In this situation, the ratio has simply been divided — a 4:3 aspect ratio can be expressed as 4/3 = 1.33. Likewise, a 16:9 aspect ratio can also be 16/9 = 1.78. Even less commonly, this might be turned back into a ratio, such as 1.33:1 or 1.78:1. That might seem confusing, but mathematically, a length of 1.33 and height of 1 is the same thing as a length of 4 and a height of 3.
Common aspect ratios
There are a lot of aspect ratios in common use today because each aspect ratio has a specific use. Here are some of the most common:
- 1:1: This is simply a square, and while there are a lot of reasons to have a square image, it is commonly used in images on social media.
- 3:2: This is a common size for sensors found in cameras and phones for shooting still images and video.
- 4:3: This was the aspect ratio used by broadcast television until the age of high definition.
- 16:9: This has become the standard aspect ratio for computer displays and cinema, though there are many exceptions to the rule.
- 2.35:1: This extra-wide aspect ratio is known as CinemaScope and is often used to make films for cinema.
Why aspect ratio is important
Aspect ratio can be important for the very reason that there are so many standards. For example, software developers creating content for both smartphones and PCs need to account for the fact that a smartphone display has a different aspect ratio than a laptop screen (many iPhones, for example, have a 9:19 vertical aspect ratio, versus the 16:9 horizontal display common on laptop screens).
The aspect ratio can even vary on a PC depending on what monitor it's paired with. Older, square-looking monitors used a 4:3 aspect ratio, while mainstream monitors are more typically 16:9. Super-wide monitors can have aspect ratios as wide as 32:9. Thankfully, the computer's operating system can accommodate multiple aspect ratios and adjust to fit whatever monitor is connected.
Not all monitors use the same aspect ratio. Some super-wide monitors have truly enormous aspect ratios. Matthew Roharik/Getty Images
Photographers and videographers might need to change the aspect ratio of a photo through cropping. For example, the Adobe Photoshop crop tool lets you change the aspect ratio after the photo has been taken.
You can use the crop tool in a photo-editing program like Photoshop to change an image's aspect ratio. Dave Johnson/Insider
Dave Johnson
Freelance Writer
Dave Johnson is a technology journalist who writes about consumer tech and how the industry is transforming the speculative world of science fiction into modern-day real life. Dave grew up in New Jersey before entering the Air Force to operate satellites, teach space operations, and do space launch planning. He then spent eight years as a content lead on the Windows team at Microsoft. As a photographer, Dave has photographed wolves in their natural environment; he's also a scuba instructor and co-host of several podcasts. Dave is the author of more than two dozen books and has contributed to many sites and publications including CNET, Forbes, PC World, How To Geek, and Insider.
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