Your guide to screen size: Aspect ratio, resolution, and more

It's time to buy a computer (or several) for your business and you'd like to be able to make an informed purchase. Factors like storage and processor speed are relatively self-explanatory, but when it comes to the display, there are a whole bunch of terms that aren't intuitively obvious. Sure, it's clear that a 13-inch display is smaller and will weigh less than a 15-incher, but what about all those other terms? 

In this piece, we'll help you understand terms like aspect ratio, resolution, PPI, and pixel pitch. We'll also help you understand how those terms describe the computers you're considering, and how you can use the numbers behind those terms to help make an informed buying decision that will pay off most effectively for your operation.

Although these terms seem arcane, within about five minutes it'll all be crystal clear, so that the next display you buy will also be crystal clear.

Aspect ratio

This describes how wide vs. how tall your screen and its images are. One of the lesser-known definitions of aspect is, according to Oxford Languages, "The positioning of a building or thing in a specified direction." In our case, we're looking at the direction of an image or screen. Ratio, of course, compares two numbers – in our case the width vs. the height.

The first aspect ratio that just about everyone older than 20 experienced was 4:3, which was also the ratio of old-school TVs back before HD. Folks then became familiar with the HDTV standard, 16:9, providing more of a wide-screen look and supporting the 1080p video standard.

When it comes to viewing standards, most modern videos are produced in 16:9, although, with the growth of smartphones, you'll see some tall 9:16 and even 1:1 videos.

Photograph ratios are still very often 4:3, especially from point-and-shoot cameras. Some large-format cameras shoot in 5:4, which produces 8x10-inch (technically, 10x8-inch) photos commonly used in promotion and portraiture. There are other specialized ratios for still photos. And as you probably know from your mobile device, smartphones produce photos in a variety of aspect ratios, changeable by tapping a mode button.

16:10 was very popular in early laptops, but it fell out of favor in the mid 'aughts due to the prevalence of 1080p in videos. While 16:9 is still the most common laptop display standard, 16:10 is staging a comeback in laptops like the Dell XPS 15. That's in part because 16:10 is very close to the golden ratio, also known as the divine proportion. 

The golden ratio, a ratio of a rectangle where width is roughly 1.5 times its height, has long been considered the most aesthetically pleasing. Artists from Dali to Da Vinci have used the golden ratio in their works, and architects and even scientists are incorporating it in their projects.

Standalone computer monitors come in a considerably wider range of aspect ratios. While you can still get 4:3 monitors, most monitors, like the Dell S2721Q 27" monitor, are 16:9. Some monitors offer even more screen real estate, like the curved Dell UltraSharp U4021QW and the Dell S3422DW 34" curved monitors, which both have a 21:9 aspect ratio.

Aspect ratio is one factor to consider when choosing a display. When it comes to laptops, you really only have a choice between 16:9 and 16:10, and you'll probably make the choice based on a wide variety of factors beyond just the shape of the screen. 16:10 may be a better option for a wider viewing range – enabling you to see more of a spreadsheet, for example. When it comes to desktop monitors, I'm of the belief that wider is better, but your decision will need to include cost, desktop space, and even weight (if you're using a monitor arm).

Resolution

While aspect ratio describes the ratio of width vs. height, resolution describes the number of pixels in each direction. Let's use the two 21:9 monitors we mentioned before to illustrate this. 

Both the Dell UltraSharp U4021QW and Dell S3422DW have 21:9 aspect ratios. But one is a $2,000 monitor and one is a $429 monitor. Clearly there are differences. The more-expensive monitor has a higher resolution. It displays 5,120 pixels horizontally and 2,160 pixels vertically. The less-expensive monitor displays 3,440 pixels horizontally and 1,440 pixels vertically. 

Practically, the second monitor shows less detail. While both might display the same image, the details of the lower-resolution monitor will be a bit more chunky than those of the higher-resolution monitor. Both of these monitors show images in enough detail that most people won't see the difference, but if you're a designer or artist, or you're looking at a lot of small text, you'll definitely notice the decrease in detail on the lower-cost monitor.

Pixel pitch, PPI, and size

These three tend to go together. Pixel pitch describes the size of each pixel. PPI stands for pixels per inch: the number of pixels fit into an inch of display space. If you divide an inch by the PPI, you'll get pixel pitch. Interestingly, pixel pitch is often described in millimeters while PPI is obviously described in inches. Even so, they are used to define the same thing – pixel density.

Let's go back to our two 21:9 monitors. The Dell UltraSharp U4021QW is a 40-inch display, measured from corner to corner. The Dell S3422DW is 34 inches.

The 40-inch display has a pixel pitch of 0.1815 mm x 0.1815 mm. 0.1815 mm is 0.00714566929 inches, or about 140 pixels per inch. The 34-inch display has a pixel pitch of 0.23175 x 0.23175 mm, which calculates out to about 110 pixels per inch. In other words, the smaller monitor has about 78 percent of the resolution of the larger.

PPI and pixel pitch are great ways of cutting through the confusion inherent in comparing monitor sizes, and they give you a size-independent way to compare pixel density.

Making a decision

It's worth noting that laptops often have higher PPIs than bigger monitors. If you're doing a lot of high-resolution photo editing, for instance, the PPI of a 'mainstream' monitor might prove problematic when you're looking at the image on the display vs. on the laptop. 

There are other factors relating to colors, viewing angle, and brightness you might want to factor into your buying decision, too. We'll cover them in a future article.

For now, consider this. If you're buying a laptop, the size of the screen is probably the most important factor, so decide that first. Screen size often informs the weight and dimensions of the machine, as well. Bigger machines have room for more ports and bigger batteries, but they can weigh down your travel bag.

If you're buying a desktop monitor, screen size is also important, but you're usually choosing based on either budget or how much information you want to display. I'm partial to ultrawide displays, but whether you go the route of more monitors or wider monitors, the amount of display real estate does impact productivity.

Once you've made a size decision, you'll have the tools to learn about display quality and pixel density. More pixels is generally better for viewing images and text.

Here's a performance tip: if you want to use all the resolution of a super-dense screen, make sure you choose a processor and display chipset beefy enough to push all those pixels to the display. My general guideline is that base-level chipsets don't match well with super high-resolution displays, but more-powerful chipsets can handle denser displays with more pixels.

Stay tuned for more on this important topic!