Well, it is a good question; glad you asked. Aspect ratio is quite simple; it is the relationship between the width and height of an image. Or, more specifically, for each height unit, there are specific units of width. You will usually see it represented as two numbers separated by a colon. For example, 16:9 is a common ratio, where 16 is the width, and 9 is the height. However, that can often be misleading. Since the number is a ratio, it represents the size but is not necessarily the actual size. Meaning, the proper size may be larger, like 64 inches long and 36 inches high. However, through the magic of mathematical reduction, you will see it as 16:9. 

You may come across an aspect ratio specification not represented in ratio form but instead shown as a single number. In these cases, it is a simple ratio division to reflect at a single value. For example, an aspect ratio of 16:9 can also be shown as 1.78, which is simply 16 divided by 9. It’s not so common nowadays, but certainly possible that you will come across it in your travels. From time to time, you may also see the height represented as a :1 along with the divided value or, in other words, 1.78:1. Which is the same as the 1.78 or 16:9. Generally, you will see this notation when referring to movie theater screens or CinemaScope, which is usually shown as 2.35:1.

The easiest way to visualize the aspect ratio is to think of a simple square. A square has an aspect ratio of 1:1, meaning the width and height are the same. For each 1 pixel in width, there is one pixel in height. As the width increases in relation to the height, a rectangle begins to develop. The higher the ratio, the more of a rectangle you will see. These can be seen in the standard aspect ratios from the past and present.


Why do I care about aspect ratio?

The answer really depends on what you intend to watch and how much of a cinephile you are. The most common screen aspect ratio you’ll find is 16:9, and for most people, this is the recommended ratio. Viewing shows and movies on a 16:9 aspect ratio will give you the most flexibility. You will be able to view older shows that are in standard definition with the 4:3 aspect ratio and nearly all movies and streaming services broadcast in 16:9. All of the everyday, affordable movie projectors project in 16:9. However, suppose you are a cinephile and want to watch a movie exactly as it was in the theaters, and you own an anamorphic lens. In that case, an aspect ratio of 2.35:1 is for you; this is also known as cinemascope.

Having a mismatch between your screen size and the intended aspect ratio of the film isn’t the end of the world. In nearly all cases, you will still be able to watch the movie. Still, you won’t do so without what I call the “bars of annoyance,” or more commonly known as black bars or letterboxing. Technically speaking, the bars on the side of the screen are pillarboxes or reverse letterboxes, and the bars on the top are letterboxes; but I digress. I’m sure you’ve seen these in your movie-watching career; bars shown on either side of the picture, top & bottom, or both. This is the screen’s way of dealing with a mismatch in aspect ratios. So while it certainly isn’t the end of the world, it can be annoying and certainly detract from viewing pleasure.


Wait, wait, is this the same as resolution?

You are full of great questions today. Well, resolution is related to aspect ratio but not the same thing. Resolution is expressed in a “by” format – pixels in width X (by) pixels in height; for example, 1920×1080. This is a shorthand notation for the 1920 pixels wide by 1080 pixels high. This represents the total pixels in the screen or image; the more pixels, the higher the resolution or more detailed images. For you math geniuses out there, you may look at 1920×1080 and realize the relationship between units of width and units of height is 16:9. In other words, the resolution of 1920×1080 is designed for an aspect ratio of 16:9. So you can see, the two work together to show the images. If you have a resolution to aspect ratio mismatch, you will be subject to the bars of annoyance, a.k.a letterboxing. <insert table aspect and resolution>

Aspect RatioTypical ResolutionsVideo Type
1:11920×1920Computer Monitors
3:22160×1440Older smart phones
4:31027×768, 2388 × 1668, 2160 × 1620Standard-definition television (SDTV), iPad 10.2″, iPad Pro 11″
5:41280×1024Standard-definition television (SDTV)
16:91920×1080High-definition television (HDTV), Many Smart Phones
16:101920×1200 High-definition television (HDTV)
19.5:92532 × 1170, 2532 × 1170iPhone 13, iPhone 12
1.85:14096×21604k cinema
2.35:13440×1440Cinema in anamorphic formats

So what aspect ratio is best for outdoor movies?

In the end, it really comes down to your personal preference and supporting equipment. That said, for most people, I would recommend a projector and screen designed with 16:9 in mind. This is the most common aspect ratio and will be suitable for pretty much all uses: movies, broadcast television, streaming, console gaming, etc… In addition to being the most commonly found aspect ratio, it is also the most affordable without sacrificing image quality and the addition of “the bars of annoyance.” The outdoor movie projectors we recommend to our readers have an aspect ratio of 16:9. However, if you have interest in more specialized projectors, stay tuned; we are working on finding the best ones as we speak.

Wrapping it all up

Aspect ratio isn’t as confusing as it may seem if you are new to building your theater setup. Really, it is little more than how the length of the width compares to the size of the length of the height. When it comes to the impact on outdoor movie projector selection, you need to decide what level of black box you are comfortable with. Some folks will tell you there is only one right choice, but I disagree. The only thing that really matters is that you are happy with your experience and equipment. That said, if you are still on the fence and really can’t decide what is right for you, 16:9 is the right path to start down.