Unlike MSRP or megapixels, there are as many ways to calculate screen sharpness as ways to eat a Reese’s. Do you factor in viewing distance? Does a larger screen make up for a slightly lower pixel density? Perhaps the safest comparison is pixels per inch (PPI), which requires precisely zero subjectivity. Here, for example, are 10 of the most popular phones ranked by PPI.
For comparing within a given product category, PPI is great. But what if we were to compare across product categories, like an HTC One next to a MacBook Pro, or a Kindle Fire HDX against a 4K TV? Given the sizable gap in viewing distances and screen sizes, a straight-up PPI comparison is no longer fair.
Instead, we calculated pixels per degree (PPD), the geeky, misunderstood cousin of PPI, which attempts to factor in viewing distance. If you picture a long, skinny triangle running from your eye (with an angle of exactly one degree) down to the screen you’re looking at, the PPD of that device is the number of pixels making up the base of that triangle.
Of course, the triangle’s base will grow larger if you move back from the screen, so this is where subjectivity comes into play. How do we know what the “standard viewing distance” is for an iPhone vs. an iPad vs. a MacBook Pro? In order to calculate PPD across product categories, we’ll need to make some assumptions about the optimal viewing distance for using each device.
When Steve Jobs first introduced the Retina iPad (early 2012), his team rather casually claimed that the standard viewing distance was 10 inches for a phone and 15 inches for a tablet. This is probably close, but it’s pretty unscientific. We weren’t satisfied with these numbers. In order to make a fair comparison, we looked at a variety of viewing charts from TV manufacturers, averaged the optimal viewing distances together, and came up with a best fit line to match their recommendations. We ended up with this:
|Device screen size||Ideal viewing distance|
|5 inches||15.9 inches|
|10 inches||26.7 inches|
|15 inches||37.5 inches|
|20 inches||48.3 inches|
|25 inches||59.2 inches|
|30 inches||70 inches|
This is clearly the most subjective part of the exercise—naturally, some people hold even their 6-inch phablets a mere 8 inches from their nose. Putting aside future eye surgery patients, we wanted to keep things simple. Yes, there is probably some fuzziness on the low and high end of this spectrum, but for today’s ranking, we assumed the ideal viewing distance would increase linearly alongside an increase in screen size.
20. iPad 2 - 60 PPD
19. iPad Mini - 63 PPD
18. Kindle Fire HD - 76 PPD
17. iPhone 5s - 78 PPD
It’s no surprise to see the iPad 2 and iPad Mini so low on this list: they're older products sporting outdated display technology. The latest iPhone, however, doesn’t do much better. It may have the classic Retina Display, but the 5s ranks behind just about every other top-shelf competitor when it comes to screen sharpness.
Note that Apple’s popular 53 PPD threshold for the Retina Display won’t match our numbers, because Apple assumes customers view their iPhones from 10 inches away, while our model pegs it at 13.7 inches.
A Little Blurry
16. Nokia Lumia 1020 - 84 PPD
15. Microsoft Surface 2 - 102 PPD
14. Nexus 7 - 114 PPD
Less interested in the pixel arms race, these products prefer to focus on camera quality (Lumia), portability (Nexus), or kickstands that sound like luxury car doors (Surface).
13. Galaxy Note 3 - 117 PPD
12. iPad Air - 120 PPD
11. Galaxy S4 - 121 PPD
10. Galaxy S5 - 121 PPD
9. Sony Xperia Z - 122 PPD
8. LG Nexus 5 - 122 PPD
Sharp enough to avoid any criticism, these products hit the industry sweet-spot—they look great, but don’t push it. Note that the three latest Samsung flagship phones fall into this category. The Galaxy phone line takes a lot of grief for chasing meaningless specs, but with screen sharpness, Samsung seems to have made a thoroughly reasonable, level-headed choice.
7. HTC One - 124 PPD
6. iPad Mini with Retina Display - 125 PPD
5. MacBook Pro with Retina Display -130 PPD
The HTC One leads all other top selling smartphones in both standard PPI and PPD, an impressive feat for a phone nearly a year old.
Meanwhile, the iPad Mini with Retina Display virtually maintains the iPhone 5s’s pixel density on a screen nearly twice the size (7.85 inches vs. 4 inches), giving the latest Mini a particularly impressive 125 PPD. But it still can’t quite match the Retina MacBook, which boasts a 232 PPI display across 13 full inches of screen real estate. Until the company releases a 4K monitor, that’s as impressive as Apple’s screens get.
4. Samsung Galaxy Note 10.1 - 140 PPD
3. Kindle Fire HDX - 144 PPD
With a 299 PPI over 10.1 inches of screen, the Galaxy Note 10.1 bests almost every other popular tablet in PPD. Surprisingly, the Amazon Kindle Fire HDX sneaks ahead, with a crazy 339 PPI over 8.9 inches of screen, which makes for a stunning 144 PPD. Those who have mentally categorized the Kindle as “just a device for reading books” may want to take a second look.
2. 55” 4K TV - 174 PPD
1. 31.5” 4K Computer Monitor - 181 PPD
So-called 4K resolution devices get their name for having a horizontal pixel count of 3,840 pixels—just shy of 4,000 (hence, 4K). That ends up being four times as many pixels as required to run 1080p high definition video, but that won’t stop TV and monitor manufacturers from setting the new standard in sharpness.
A 55” 4K TV—when viewed from over 10 feet away—achieves an impeccable 174 PPD, enough to beat out any smartphone or tablet on the market. A 31.5” 4K computer monitor, however, presents a whole new level of insane. With a 3,840 x 2,160 resolution packed into just 31.5 inches, the screen is both giant and incredibly sharp, earning a ridiculous 181 PPD.
Granted, there are a few caveats here. First, that 181 PPD assumes you’re sitting back about six feet from the screen—say, to watch a movie or view photos as a group. When you’re at your desk working away, that PPD will decrease. Second, 4K monitors might be a little too good to buy today—most of the web hasn’t optimized for that kind of resolution yet, and 4K monitors aren’t smart enough to scale low-res content the way 4K TVs do.
Still, a 30+ inch screen with that kind of pixel density (~120 PPI) is nuts, and it’s enough to make the 4K computer monitor the most impressive display on the market...for now.
This article was written for TIME by Ben Taylor of FindTheBest.