What Is Aspect Ratio? 21:9, 16:9, 4:3 (Ratio Calculator)

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What is Aspect Ratio? It’s one of the terms you come across when buying TVs. If you don’t know it, you and the salesperson may not understand each other. 

I’ve been there, too! But then, I realized that understanding a bit of its aspect ratio can change my experience. So, if you are curious about it, scroll down to see what I have found out! 

What Is Aspect Ratio?

The aspect ratio of a monitor is the ratio between its width and height. Thus, it’s written as W:H, with W referring to the width and H for the height.

So, if you know a TV’s aspect ratio, you can picture its shape in mind. This specification will affect your movie-watching experience, too. 

What is aspect ratio

Most TVs these days offer a ratio of 16:9. Meanwhile, in the past, the 4:3 ratio was common. This rate means old TVs are squarer than modern ones. I will discuss some popular aspect ratios in TVs now. Then, you can understand more about the importance of this feature. Let’s have a look at your options first!

Aspect Ratio Calculator

Aspect Ratio Table

Aspect Ratio 16:9 4:3 21:9
Uses HD Channels SD Channels Most movies
TVs Most HDTVs Old TVs Few TVs and PC monitors 
Associated Resolutions  1280×720

16:9 Ratio

16:9 is the most common aspect ratio
16:9 is the most common aspect ratio

People have used this aspect ratio for computer monitors and televisions. It’s also the global standard format for Full HD, UHD, and HDTV today. 

The 16:9 ratio means the TV’s horizontal area is wider than the vertical. This format is popular because: 

  • Monitors of this widescreen aspect ratio offer a high resolution, which can be from 720 x 576 to 1920 x 1080 pixels. 
  • Compared to its older versions, this ratio makes it easier to create cost-effective displays. 

4:3 Ratio

TVs in this fullscreen aspect ratio are often short. People used such TVs a lot until the end of the 20th century.

During that time, filmmakers shot videos at the 4:3 ratio. It was also the only option for computer monitors, TV sets, and other screens back then. 

21:9 Ratio 

21:9 TVs came out a few years ago to serve movie fans. They are well-suited for streaming movies, allowing you to enjoy the realistic pictures. However, these TVs are usually more expensive, even at that time.

What Is IMAX Aspect Ratio? 

IMAX theaters and movies have their own rules. For example, they need specialized cameras, room designs, screen setups, and sound systems to give you the best experience. 

Two aspect ratios in IMAX
Two aspect ratios in IMAX

Another unique feature of IMAX is its movie screen. There are two main aspect ratios used in IMAX: 

  • 1.9:1 – Digital theaters prefer this ratio, which is also the standard for digital projectors. 
  • 1.4:1 – This screen is tall and quite square. These features make IMAX so iconic because the screens are larger than those in regular cinema theaters. The height will make you immersed in the epic movie scenes.  

If filmmakers use IMAX technology, they often combine 1.4:1 and 21:9 ratios. The pictures go taller than a regular TV, but they can get cut off to fit the screen. 

Why Should You Use The Right Aspect Ratio?

The right Aspect Ratio is important for your smooth viewing experience. If the aspect ratio of the content doesn’t match that figure of your TV, you will see black bars on the screen. These bars can be vertical or horizontal, depending on the difference between the display’s ratio and the picture. 

black bars

For example, if you display a 21:9 movie on a 16:9 screen, black bars will show up at the bottom and top. 

The best solution for this issue is to use the screen with the right aspect ratio for your content. Otherwise, you can crop the picture; however, this method may also remove some parts of it. Another idea is to stretch the screen. Unfortunately, it may distort the pictures while trying to fit the screen. 

The solution also depends on the TV brand you use. For example, if you have a Sony TV, it allows you to stretch the screen fully and zoom it. You can even do these two things at the same time. 


The aspect ratio can reveal the shape of a monitor. If it doesn’t match the content, you will see the black bars on the screen, it can affect your experience.

So, learning about the aspect ratio can help you set up the best streaming system for your gaming and movie time. Then, you can choose the perfect aspect ratio for the entertainment needs!


Pete is a software engineer who currently works full-time managing MarsScreen.com. On the side, he enjoys coding his own projects and spending time with his wife and two dogs. When he's not working or hanging out with family and friends, you can find him playing the guitar or running. My Instagram.

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