What is PPI? Does pixel density matter?

What is PPI? Does pixel density matter?

Have you ever wondered what PPI is? Maybe you’ve heard companies discussing high PPI screens and wanted to know what that is. Why are some manufacturers bragging about their high-end devices with huge pixel-density screens? Why does PPI matter so much, especially when referring to smartphones? Read this article, and you’ll find out what it means, whether PPI and DPI are the same, and whether this measurement matters when talking about screens of all sizes:

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What is PPI (Pixels Per Inch)?

PPI is the acronym for Pixels Per Inch. It is a unit of measure used to quantify the number of pixels found on a square-inch surface. To get a clear idea of what it means, imagine a square inch that’s divided and organized in a grid of cells. Each and every cell in that grid has a pixel inside. The number of cells inside the grid, also known as pixels, tells you the PPI.

What is PPI (Pixels Per Inch)?

What is PPI (Pixels Per Inch)?

The term Pixels Per Inch (PPI) commonly refers to the measurement of pixel density in display screens, including those of computers, laptops, TVs, and smartphones. This metric helps you determine the sharpness and clarity of the image you see on the screens of these devices.

PPI is a metric used for all kinds of screens

PPI is a metric used for all kinds of screens

A higher PPI means more pixels are packed into each inch of the screen. In other words, a higher PPI density means a finer, more detailed display. Therefore, the PPI value of your device’s screen tells you a lot about the quality of the visual output it can produce.

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Are PPI and DPI the same?

Not quite. While PPI stands for Pixels Per Inch, DPI represents Dots Per Inch. Common sense will probably lead you to believe they’re different. And you’d be right! Although both terms refer to density, and you could easily confuse pixels with dots (probably because they’re so tiny), PPI and DPI are different things. While PPI refers mostly to screens and digital elements, DPI is a term used correctly when referring to things like printed paper.

PPI versus DPI

PPI versus DPI

Image source: Wikipedia

A printed paper's resolution and quality are rightly measured by the number of ink dots in any given character or drawing. DPI and PPI measure similar things, but dots are not pixels, and pixels are not dots, so DPI is not the same. However, PPI and DPI are often used to describe the same thing. It’s not correct, but big companies like Google and Microsoft, as well as many hardware manufacturers, often use these terms interchangeably, and thus, people started to use them loosely, too.

Does PPI matter when choosing your mobile phone, TV, or computer display?

Yes, it does. When you buy a new smartphone, computer monitor, TV, or any other type of device with a display, you want its screen to look as best as possible, right?

Let’s say that you want to get a new smartphone, and after looking around the internet, you decide that you like the Xiaomi 14 Ultra and the Sony Xperia 1 VI. Money doesn’t matter to you - what does matter, however, is the screen of your next smartphone. The Xiaomi 14 Ultra has a 6.73-inch display, a resolution of 1440 x 3200 pixels, and a pixel density of 522 PPI. The Sony Xperia 1 VI has a 6.5-inch screen, a resolution of 1080 x 2340 pixels, and a pixel density of 396 PPI. The screen size, the resolution, and the PPI pixel density of the Xiaomi 14 Ultra are significantly higher than what the Sony Xperia 1 VI has to offer.

PPI density on mobile phones

PPI density on mobile phones

TIP: If you’re curious about your screen’s pixel density, here’s a handy PPI calculator.

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That means a lot more pixels are spread across its screen surface. I can’t draw 522 pixels, or even 396, in an image the size of an inch because you wouldn’t see them. But here’s an illustration of what different PPI densities look like:

What PPI means

What PPI means

So wouldn’t you choose the smartphone with the higher PPI, the Xiaomi 14 Ultra? A higher PPI, or pixel density, means you get a lot more detail for anything displayed on your screen. Which means better images, better fonts, smoother lines, or, in other words, higher quality. Everybody wants that, right?

Can the PPI density get so high that it becomes meaningless?

Although a higher PPI is always theoretically better, before making any purchase, you should also know that the human eye is probably not able to perceive any differences in a PPI that’s higher than a certain limit. However, when it comes to determining the exact limit when the human eye stops being able to see more details on a screen and the pixel density stops being important, that is a matter of debate.

For now, neither researchers nor ordinary people can give you a straight answer and say that “pixel density becomes meaningless after, say, a value of 500 PPI.” However, according to the Fundamentals of Digital Imaging in Medicine by Roger Bourne, the magic number would be 400 PPI if you look at an image found roughly 16 inches or 40 cm from your eyes. That’s because the human eye has 400 sensor cells per millimeter of retina surface.

400 to 450 PPI is good for mobile phones

400 to 450 PPI is good for mobile phones

Which is also probably the main reason why today’s smartphones, for instance, no longer emphasize on pixel density and high resolutions (such as QHD and 4K). While that was a trend a couple of years ago, in present times, manufacturers prefer to stick to FHD+ resolutions for the displays on the mobile phones they make.

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A 395 PPI density is good (or not bad, at least) for a smartphone screen, allowing fine image quality while also keeping power consumption at acceptable levels. Higher-resolution displays with higher PPI aren't always better. What matters more is achieving the right balance between resolution, size, PPI density, and other methods of enhancing display quality, like incorporating HDR content and higher refresh rates.

Screen quality factors in other specs beside PPI

Screen quality factors in other specs beside PPI

Eizo also has an excellent article called Confused about HiDPI and Retina display? ― Understanding pixel density in the age of 4K, in which you can find a few tables with data showing the screen resolutions and pixel densities used today.

Manufacturing companies calculate most of the pixel density values used on modern displays, be they smartphone displays, tablet displays, or computer monitors, depending on the viewing distances (the distance from the eye to the front surface of the screen) used by most people. In the end, pixel density certainly matters, but regardless of how companies market their products, don’t start spending money until you see what the screen of your next device actually looks like.

Will you look for a high PPI density on your next devices?

I’m curious: now that you know what PPI means and how it affects screen quality, will you take it into consideration the next time you buy a TV screen, a computer monitor, or a new smartphone? Or are you more interested in other image quality details such as HDR or refresh rate? Let me know in the comments section below.

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