What is the Aspect Ratio? (4:3, 16:9, 21:9)

Updated Jan 27, 2014 By Cedric Demers

The aspect ratio is the proportion between the width and the height of a picture. It is often expressed in the W:H format, where W is the width and H the height. For example, a 16:9 aspect ratio means that for a width of 16 units, the height must be 9 units.

Aspect RatioUsesTVs
4:31.33:1Standard ChannelsOld TVs
16:91.77:1HD ChannelsThe majority of HDTVs
21:92.35:1Most moviesVery few TVs
The most common aspect ratios in the video industry.

Most televisions and computer monitors currently available have an aspect ratio of 16:9, which fits perfectly the high definition television shows. However, movies are usually filmed with a ratio of 21:9, which will results in black bars at the top and bottom of the picture. To fix this, some manufacturers are producing televisions with a 21:9 format. The table shows the most common aspect ratios.

In theaters, this is why the screen widens at the beginning of a movie. Ads shown before the movie have an aspect ratio of 16:9, while the movie itself is 21:9.

What does black bars looks like on different aspect ratio TVs?

Black bars on different aspect ratio
Black bars are filling the extra space when the aspect ratio does not match.

The position and size of black bars on your television depends on two factors: the aspect ratio of your television and the aspect ratio of the video you are watching. Any mismatch between the two will be filled by the black color. This practice is called letterboxing. The following picture shows the black bars for different televisions and aspect ratios (4:3, 16:9 and 21:9). All televisions have the same diagonal length.

If you do not like having black bars, you have two options available in the settings of your TV: cropping or stretching. Cropping the picture is the equivalent of zooming, but it will remove the sides of the picture. Stretching retains all information, but the proportions are not kept.

As you can see, when you watch a 21:9 movie on a normal 16:9 widescreen TV, you will have some black bars at the top and bottom. This is represented by the top center TV in the illustration.

Is a 21:9 TV Worth It?

Comparaison between 21:9 CinemaWide and 16:9 television
A 58" 21:9 TV is equivalent to a 61" for 21:9 media, but only 47" for 16:9 media.

TVs with a 21:9 aspect ratio are rare. A 21:9 TV is only worth it if you watch almost exclusively movies (more than 80% of the time). If you watch a normal 16:9 content (like a HDTV channel) on it, you will see black bars on the sides. This reduces the viewing area for 16:9 content considerably. A 58" 21:9 television correspond to the same viewing area of a 47" for 16:9 content, as you can see in the illustration.


The most common aspect ratio of TVs and monitors is currently 16:9, which also correspond to the aspect ratio of TV shows. However, movies usually have an aspect ratio of 21:9, which will result in black bars above and below the picture if you watch it on your 16:9 screen.


Jan 27 2014
When I download a 1080p movie, the resolution is not 1920x1080 but 1920x800 and there are black bars on my screen. Why?
This is normal. The official resolution of a 1080p Blu-ray is indeed 1920x1080 which correspond to an aspect ratio of 16:9. However, most movies are shot in 21:9 instead. To fit this on the Blu-ray format, black pixels are used at the top and bottom of the picture. When encoded for the internet, most people strip those black bars which result in a 1920x800 resolution.
Feb 27 2014
I'm really considering the Lenovo B750, which has a wide screen 21:9 to be exact. I would maybe watch some bluray DVDs on it from time to time. I really like the idea of more real estate while surfing web. Guess I am just nervous since some people like and some dislike.
We haven't reviewed that monitor (we only review TVs currently). The additional real estate when surfing the web isn't really useful in 21:9 though, because there are no website designed for this. Therefore, you will most likely browse the web not full screen, which kind of defeat the purpose of the extra wide screen.
Sep 03 2014
How much area are the letterbox bars supposed to cover on a 16:9 tv?
It depends on the aspect ratio of your media. If it is a 21:9 movie, the bars are a few inches tall, as shown in the illustration above.
Sep 16 2014
If 16:9 ratio has resolution 1920x1080, what resolution has 21:9 ratio? When I use a 21:9 ratio monitor with resolution 2560x1080 (LG 34UM65-P), is the picture of movie then ok? What resolution shows the monitor the movie? 1920x1080 or 2560x1080?
1080p 21:9 movies have a resolution of 1920x800. Your monitor has more pixels than a movie. When you view a movie full screen on it, the video is upscaled 1.35 times (both directions), so it will fill all 2560x1080 pixels. This is not an issue, even if there is no 1:1 pixel mapping.
Oct 13 2014
What is the widescreen aspect ratio? 21:9?
16:9 is generally considered widescreen.
Aug 04 2014
Does a 4k TV have a 21:9 ratio?
No. A 4k TV has a ratio of 16:9 (3840x2160).
Sep 08 2014
I have 65 inch tv in 16:9 full pixel mode the letter box bars are about 4 inches each when playing 21:9 movies, which comes out be approximately 25 % of the screen. In comparison with my old 60 inch it appears the bars are covering a lot more area, is this possible or I am just analyzing too much?
In full pixel mode, this sounds about right. You can always choose a zooming/cropping option if you don't want to bars to show, but you will lose part of the picture.
Oct 11 2014
On my 32 inch TV, I notice that a 720p/1080p video plays and looks fine meaning that the people, animals etc look proportionate. However on a 23 inch TV, I have noticed that when playing any 720p/1080p videos, the people, animals etc look stretched vertically when covering the full portion of the screen. My question is are there standard sizes like 32 inch, 40 inch, 60 inch etc on which the proportion of the people, animals will look just fine without having to stretch or crop etc? If yes, what will be the best method to know it?
It doesn't depend on the size of the TV, but of its aspect ratio. Assuming you have a 16:9 23", the problem might just be the crop/stretch/zooming option. Look for a setting named 'Picture Size' or something similar and try different values.
Oct 23 2014
When talking of ratio aspects can you explain why we have 1.33:1 for example?
1.33:1 is just 4:3, but normalized (4 divided by 3 equals 1.33).
Oct 23 2014
What is 2K?
2K is just another term for the 1080p resolution, because it is 1980 pixels wide (almost 2k).
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