As Fast As Possible
Pixel density indicates how many pixels per inch (PPI) are there on a display. The higher the pixel density, the more detailed and spacious the picture is. In contrast, displays with low pixel density will have less screen space and more pixelated image quality.
In short, pixel density is the ratio between a screen’s size and its resolution.
For instance, the standard 1920×1080 Full HD resolution will result in a different pixel density (or pixel-per-inch ratio) on a 24″ screen (92 PPI) and on a 27″ screen (82 PPI).
More pixels per inch mean more screen real estate as well as sharper and clearer details. If a display has a too low pixel density, there will be limited screen space available while the picture will be pixel-y and fuzzy.
In case there are too many pixels per inch on a screen (over 110 PPI on desktop monitors), everything will be tiny, so you will need to apply scaling in order to increase the size of small items such as text to a readable level.
Pixel Density & Viewing Distance
Having the highest pixel density possible isn’t always better or even necessary. If you’re looking for a gaming monitor, high pixel density requires high screen resolution which in turn demands more processing power and therefore has an impact on the frame rate.
Further, certain applications don’t scale well. For instance, if you have a 27″ 4K monitor (163 PPI), you may find 150% scaling to be ideal for you whereas some applications will only scale to 100% and 200%.
This will leave you with things being either too small or too big in that application. Luckily, most apps have improved their scaling support since the high-resolution displays had first appeared on the market.
Note that at a certain viewing distance, the human eye cannot distinguish pixels from one another. Just how far away from the screen you’ll need to be in order not to distinguish the pixels depends on the display’s pixel density. Apple trademarked this ideal viewing distance/pixel density ratio as ‘Retina’.
So, if you have a 24″ 1080p monitor with a pixel density of roughly 92 pixels per inch, you will need to be 37″ (or 94cm) away from the screen; at this distance, your eyes won’t be able to distinguish the pixels on the monitor.
In other words, at 37″ (or further) viewing distance, a 24″ 1080p monitor is ‘Retina’. In case you have a 27″ 1080p monitor, you’d need to be 42″ (107cm) away from the screen, and so on.
You can visit this website and calculate at what distance certain screen size/resolution becomes retina or check the table below which consists of the most common monitor size/resolution combinations and their corresponding optimal viewing distance.
|Screen Size||Screen Resolution||Pixel Density||Optimal Viewing Distance|
|24”||1920×1080||92 PPI||37” (94cm)|
|24”||2560×1440||122 PPI||28” (71cm)|
|24”||3840×2160||184 PPI||19” (48cm)|
|27”||1920×1080||82 PPI||42” (107cm)|
|27”||2560×1440||109 PPI||32” (81cm)|
|27”||3840×2160||163 PPI||21” (53cm)|
|32”||1920×1080||70 PPI||49” (124cm)|
|32”||2560×1440||93 PPI||37” (94cm)|
|32”||3840×2160||140 PPI||25” (64cm)|
|29” UltraWide||2560×1080||96 PPI||36” (91cm)|
|34” UltraWide||2560×1080||82 PPI||42” (107cm)|
|34” UltraWide||3440×1440||110 PPI||31” (79cm)|
|38” UltraWide||3840×1600||111 PPI||31” (79cm)|
|43”||3840×2160||104 PPI||33” (84cm)|
For the best viewing experience, we recommend displays with a pixel density close to 110 PPI. At this pixel per inch ratio, you get plenty of screen space and sharp details without having to use any scaling.
Of course, if you want a better image quality, aim for higher pixel density. We advise against getting a monitor with a pixel density that’s lower than ~90 PPI unless there’s no alternative.
When it comes to TVs, you can see how 1080p and 4K resolution compares in terms of viewing distance and pixel density in this article.
Rob is a software engineer with a Bachelor’s degree from the University of Denver. He now works full-time managing DisplayNinja while coding his own projects on the side.