Answer:
Pixel density indicates how many pixels per inch (PPI) there are on a display. The higher the pixel density, the more detailed the picture is.
In contrast, displays with low pixel density will have a more pixelated image quality with duller details.
A monitor specification that’s often overlooked and lost in the more protruding specs, such as refresh rate and panel type, is the pixel density.
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 pixels per inch) on a 24″ screen (92 PPI) and on a 27″ screen (82 PPI).
Even though you will get the same amount of screen real estate, more pixels per inch means sharper text and clearer fine details!
If a display has a too low pixel density, the picture will be pixely and fuzzy.
In case there are too many pixels per inch on a screen (over 140 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 the better solution or even a necessary one. 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% or 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 high-resolution displays first appeared on the market.
If you’re using older software, however, make sure to check its scaling compatibility before getting a monitor with high pixel density.
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 recognize the pixels depends on the display’s pixel density.
NOTE
Apple trademarked this ideal viewing distance to 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 in order for your eyes not to 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 for it to be ‘Retina’, and so on.
You can visit this website and calculate at what distance a certain screen size/resolution becomes retina or check the table below, which consists of the most common monitor size/resolution combinations and their 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) |
| 39″ UltraWide | 3440×1440 | 95 PPI | 36″ (91cm) |
| 40″ UltraWide | 5120×2160 | 140 PPI | 25″ (64cm) |
| 45″ UltraWide | 3440×1440 | 82 PPI | 42″ (107cm) |
| 45″ UltraWide | 5120×2160 | 123 PPI | 28″ (71cm) |
| 43″ | 3840×2160 | 104 PPI | 33″ (84cm) |
| 49″ 32:9 | 5120×1440 | 109 PPI | 32″ (81cm) |
| 49″ 32:9 | 3840×1080 | 81 PPI | 42″ (107cm) |
| 57″ 32:9 | 7680×2160 | 140 PPI | 25″ (64cm) |
What’s the bottom line?
For the best viewing experience, we recommend displays with a pixel density between ~110 and 140 PPI. At this pixel density, you get sharp details without having to use any scaling.
Of course, if you want better image quality, aim for higher pixel density.
We advise against getting a monitor with a pixel density that’s lower than ~80 PPI unless there’s no other alternative, though a lot of people would argue that anything below 90 PPI is too low.
We find that ~80 PPI is okay for gaming and content consumption, but not for work, especially if you need a lot of screen space and sharp text.
When it comes to TVs, you can see how 1080p and 4K resolutions compare in terms of viewing distance and pixel density in this article.
