What we’ve just learned about how the Apple Watch works

“Developers can now make apps for Apple Watch,” Ross Miller reports for The Verge. “Well, they’re not separate apps so much as they are extensions of pre-existing iPhone apps, and there isn’t a lot of flexibility in the WatchKit toolset — but it looks like that’ll change next year.”

“An iPhone is required — at (almost) all times,” Miller reports. “[But] native apps are coming next year.”

“The resolution[s] for Apple Watch’s two ‘Retina displays’ [are now known],” Miller reports. “The UI documentation revealed that the smaller, 38mm device will be 272 x 340 pixels and the larger, 42mm one will be 312 x 390 pixels. That comes out to the same aspect ratio (4:5).”

Much more in the full article here.

“It also turns out there are three types of screens: Glance, Actionable Notifications, and the full, nebulous app screen with all your apps,” Malarie Gokey reports for Digital Trends.

“The Glance screens are exactly what they seem — a quick, tidbit of information you can digest and read in a single glance. Actionable Notifications allow the user to respond, go into the app, and perform other actions,” Gokey reports. “The app screen looks exactly as we saw it in September, with many tiny, circular app icons bopping about.”

Read more in the full article here.


    1. Knowing Apple, they will likely soon begin development on an assistive device, or an alternative model for persons with visual disability. Considering the complexity and subtlety of information that can be presented visually on that screen, the assistive solution is more likely to be along the lines of Siri (voice-oriented), rather than some tactile display. I won’t pretend to know anything, since I don’t know anyone who needed such a device, so I don’t have even second-hand experience.

    2. True for most watches, but not the Apple Watch. Just like all other computing devices made by Apple Inc, it will be packed with accessibility features designed for people with disabilities because that’s just how Apple operates.

  1. English major here . . . can someone do the math of PPI?

    I imagine it’s around 300 but would love to know the specifics.

    I’m not disappointed per se in that figure, as it is pretty hard to see anything smaller than that. However, given the watch’s need to mimic reality (such as with a mechanical second hand) I thought maybe we’d see something higher.

      1. Math is wrong. Here is the simple equation:

        390 pixels, divided by 42mm (gives us number of pixels per 1 mm): ~ 9.28

        9.28 times 25 (milimetres in one inch): ~232 pixels per inch

        For the small screen:


    1. For the large screen, it is 232 pixels per inch; for the smaller, it is 223 ppi. This is noticeably lower from similar handheld devices (various iPhones and iPod touches), and closer to the pixel density on Retina Macs (MBP, 5K iMac).

      According to Jobs’s statement in the presentation, 300ppi at 12 inches of distance is beyond the resolution human retina can tell apart. In constant terms, this translates into about 73 pixels per one angular degree. Depending on the viewing distance, these pixels will be bigger or smaller.

      Based on those numbers, the Apple Watch display is border-line Retina. Considering that the viewing conditions for a watch are generally far from optimal, I’m sure the sharpness and image quality of the display will be considered perfectly fine.

    2. It’s 302.04 ppi for the larger one, and 291.04 ppi for the small one.

      Here’s where I got the measurements:

      The 38mm and 48mm sizes are the diagonals, while the sizes 272px by 340px and 312px by 390px are the sides. Because the sides and diagonals are different, I used the Pythagorean Theorem to calculate the diagonal based on pixel length of sides. This makes the diagonals 435.41px and 499.44px on each screen.

      These diagonals match the 38mm and 48mm lengths given, which converted to inches are 1.49606in and 1.65354in. Now that we the length of the diagonals in both pixels and inches, simply divide the two to get the number of pixels per inch.

      435.41px / 1.49606in = 291.03779 ppi
      499.44px / 1.65354in = 302.04289 ppi

  2. 312 x 390 = 121680 pixels, (seems high)
    42 mm = 1.6535433070866 inches diagonal, (seems normal)
    4:5 = Height 1.29 x 1.03 Width = 1.33 square inches
    121680 pixels/1.33 inches = 91488 pixels per sqare inch
    no way, what did i do wrong?
    wow, did i even come close?
    anyone care to correct me? i can take a flaming for my ineptitude, as long as i learn something so i am a little more adept than inept as my day progresses !-)

      1. Your math is correct, but the dimensions are wrong. The screen is not 38mm or 42mm – those are the sizes of the watch case. Apple has not released the actually dimensions of the display.

          1. Someone did a little guesstimating and came up with a display height of around 30.5mm in the 42mm model. Which comes out as 13ppmm or 330ppi

            So, with that, I’d guess the watch displays are the same as the “Retina” iPhones at 326ppi, which makes a lot of sense.

    1. What you did wrong was calculating pixels per square inch.

      The value we are looking for was pixels per inch (linear). In other words, when you look at a square JPG image that appears to be one inch wide (and one inch tall), what are the two dimensions of this image; for an iPhone 6 plus, for example, 401 x 401 pixels.

Reader Feedback

This site uses Akismet to reduce spam. Learn how your comment data is processed.